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Wearing Blue-Blockers in the Morning Could Improve Sleep of Workers on a Permanent Night Schedule: A Pilot Study
Abstract
Night shiftworkers often complain of disturbed sleep during the day. This could be partly caused by morning sunlight exposure during the commute home, which tends to maintain the circadian clock on a daytime rhythm. The circadian clock is most sensitive to the blue portion of the visible spectrum, so our aim was to determine if blocking short wavelengths of light below 540 nm could improve daytime sleep quality and nighttime vigilance of night shiftworkers. Eight permanent night shiftworkers (32-56 yrs of age) of Quebec City's Canada Post distribution center were evaluated during summertime, and twenty others (24-55 yrs of age) during fall and winter. Timing, efficacy, and fragmentation of daytime sleep were analyzed over four weeks by a wrist activity monitor, and subjective vigilance was additionally assessed at the end of the night shift in the fall-winter group. The first two weeks served as baseline and the remaining two as experimental weeks when workers had to wear blue-blockers glasses, either just before leaving the workplace at the end of their shift (summer group) or 2 h before the end of the night shift (fall-winter group). They all had to wear the glasses when outside during the day until 16:00 h. When wearing the glasses, workers slept, on average +/-SD, 32+/-29 and 34+/-60 more min/day, increased their sleep efficacy by 1.95+/-2.17% and 4.56+/-6.1%, and lowered their sleep fragmentation by 1.74+/-1.36% and 4.22+/-9.16% in the summer and fall-winter group, respectively. Subjective vigilance also generally improved on Fridays in the fall-winter group. Blue-blockers seem to improve daytime sleep of permanent night-shift workers.
... Nonetheless, we know that blue-blockers can prevent melatonin suppression [29,[46][47][48]. They were also used in field studies in conjunction with bright light to phase-shift night worker's circadian clock [49][50][51]. It is interesting to note that previous studies using blue-blocking glasses did not observe vigilance variations, whether they were worn by night workers at the end of their shift [47,49,51] or by study participants during a driving simulator task at night [46]. ...
... They were also used in field studies in conjunction with bright light to phase-shift night worker's circadian clock [49][50][51]. It is interesting to note that previous studies using blue-blocking glasses did not observe vigilance variations, whether they were worn by night workers at the end of their shift [47,49,51] or by study participants during a driving simulator task at night [46]. We cannot, however exclude the possibility that a blue-enriched light exposure could be superior to a short wavelength-free light when used for a longer time period. ...
... The results of this study may have practical application for night workers. For instance, it was suggested by our group to wear blue-blockers after a night shift to impede the undesirable resynchronizing effect of morning sunlight on the way home, which yielded to improve daytime sleep [49,50]. The present study supports that blue-blockers should not hinder the alerting effect of sunlight when used for a short period of 30 min during a commute home. ...
... However, dynamic lighting was associated with a decrease in perceived health status [127]. Lastly, one study evaluated the effect of light-blocking glasses which resulted in increased objective sleep duration and efficiency [125]. In terms of side effects, participants reported difficultly falling asleep on days off when in the treatment condition [120] and headaches [118,124,127] and eye strain [124]. ...
... This is not surprising-while shift work may be a common feature for these workers, individual differences in occupation, sociodemographic characteristics, job demands, and health status likely call for unique interventions. Broadly, objective sleep measures were improved by controlled light exposure including intermittent bright light [123,130], bright light and light-blocking goggles [119,126,129,130], light-blocking goggles alone [125], schedule change which increased recovery periods [87,92,96] and prescriptive sleep scheduling [116]. Subjective measures of sleep were improved by a change to 12 h shifts (e.g., two-shift system) [70,88,89,91,93,97], a change to forward rotation schedules [78,80,83,90], increased rest or recovery periods [75,79], individualised behavioural intervention aimed at improving sleep and fatigue [106,115], and some complementary therapies (e.g., electrical acupoint stimulation and aromatherapy massage) [131,134]. ...
Shift work is associated with adverse chronic health outcomes. Addressing chronic disease risk factors including biomedical risk factors, behavioural risk factors, as well as sleep and perceived health status, affords an opportunity to improve health outcomes in shift workers. The present study aimed to conduct a systematic review, qualitative synthesis, and meta-analysis of non-pharmacological interventions targeting chronic disease risk factors, including sleep, in shift workers. A total of 8465 records were retrieved; 65 publications were eligible for inclusion in qualitative analysis. Random-effects meta-analysis were conducted for eight eligible health outcomes, including a total of thirty-nine studies. Interventions resulted in increased objective sleep duration (Hedges’ g = 0.73; CI: 0.36, 1.10, k = 16), improved objective sleep efficiency (Hedges’ g = 0.48; CI: 0.20, 0.76, k = 10) and a small increase in both subjective sleep duration (Hedges’ g = 0.11; CI: −0.04, 0.27, k = 19) and sleep quality (Hedges’ g = 0.11; CI: −0.11, 0.33, k = 21). Interventions also improved perceived health status (Hedges’ g = 0.20; CI: −0.05, 0.46, k = 8), decreased systolic (Hedges’ g = 0.26; CI: −0.54, 0.02, k = 7) and diastolic (Hedges’ g = 0.06; CI: −0.23, 0.36, k = 7) blood pressure, and reduced body mass index (Hedges’ g = −0.04; CI: −0.37, 0.29, k = 9). The current study suggests interventions may improve chronic disease risk factors and sleep in shift workers; however, this could only be objectively assessed for a limited number of risk factor endpoints. Future interventions could explore the impact of non-pharmacological interventions on a broader range of chronic disease risk factors to better characterise targets for improved health outcomes in shift workers.
... Based on the research reviewed one possible strategy to promote adaptation to nightwork is to use coloured lenses to block blue wavelengths while traveling home from work (e.g. dark or orange lenses) 10,12,20,24,26,27,32,40) . A suggested strategy for use of dark glasses is therefore included in the key statements below. ...
... The treatment groups of nurses were likely helped by wearing dark goggles to reduce light exposure during morning hours and other groups like police officers and oil platform workers also seem to benefit from equivalent treatments (e.g. blue blocking orange lenses) 10,32) . ...
Interventions and strategies to improve health through the management of circadian (re)adaptation have been explored in the field, and in both human and animal laboratory manipulations of shiftwork. As part of an initiative by the Working Time Society (WTS) and International Committee on Occupational Health (ICOH), this review summarises the literature on the management of circadian (re)adaption using bright light treatment. Recommendations to maximise circadian adaptation are summarised for practitioners based on a variety of shiftwork schedules. In slowly rotating night shift schedules bright light appears most suitable when used in connection with the first three night shifts. These interventions are improved when combined with orange glasses (to block blue-green light exposure) for the commute home. Non-shifting strategies involve a lower dosage of light at night and promoting natural daylight exposure during the day (also recommended for day shifts) in acordance with the phase and amplitude response curves to light in humans.
... The dim light melatonin onset (DLMO) is a more precise marker for estimating the unmasked phase position of the circadian pacemaker [100]. Furthermore, Lewy et al. [101] suggest that by using goggles that blocks short wavelength radiation [102], saliva sampling for assessment of the DLMO could be performed in the subjects' home environment. Cortisol is influenced by other factors than light. ...
... There are relatively few field studies and only the most recent studies have investigated the spectral composition of the exposing light radiation. The complex interaction of different receptor systems, with different sensitivity functions, makes spectral composition an important characteristic to consider when investigating the non-image forming effects of light radiation [102,[109][110][111][112][113]. This study add to the results from other studies investigating light exposure in real working and living environments by reporting on diurnal and seasonal light exposure patterns for a group of Swedish office workers living at a high latitude of 56? N, a location at which no similar study have been carried out. ...
Background:
Seasonal variations in physiology and behavior have frequently been reported. Light is the major zeitgeber for synchronizing internal circadian rhythms with the external solar day. Non-image forming effects of light radiation, for example, phase resetting of the circadian rhythms, melatonin suppression, and acute alerting effects, depend on several characteristics of the light exposure including intensity, timing and duration, spectral composition and previous light exposure, or light history. The aim of the present study was to report on the natural pattern of diurnal and seasonal light exposure and to examine seasonal variations in the circadian change of melatonin and cortisol concentrations for a group of Swedish office workers.
Methods:
Fifteen subjects participated in a field study that was carried out in the south of Sweden. Ambulatory equipment was used for monthly measurements of the daily exposure to light radiation across the year. The measurements included illuminance and irradiance. The subjects collected saliva samples every 4 h during 1 day of the monthly measuring period.
Results:
The results showed that there were large seasonal differences in daily amount of light exposure across the year. Seasonal differences were observed during the time periods 04:00-08:00, 08:00-12:00, 12:00-16:00, 16:00-20:00, and 20:00-24:00. Moreover, there were seasonal differences regarding the exposure pattern. The subjects were to a larger extent exposed to light in the afternoon/evening in the summer. During the winter, spring, and autumn, the subjects received much of the daily light exposure in the morning and early afternoon. Regarding melatonin, a seasonal variation was observed with a larger peak level during the winter and higher levels in the morning at 07:00.
Conclusions:
This study adds to the results from other naturalistic studies by reporting on the diurnal and seasonal light exposure patterns for a group living at a northern latitude of 56° N, with large annual variations in photoperiod length. It seems to be seasonal variation in the lighting conditions, both concerning intensities as well as regarding the pattern of the light exposure to which people living at high latitudes are exposed which may result in seasonal variation in the circadian profile of melatonin.
... One randomized study of subjects with insomnia demonstrated improvement in sleep quality and mood in individuals wearing blue wavelengthblocking glasses, compared with a placebo group (Burkhart & Phelps, 2009). Daytime use of such glasses in permanent night-shift workers resulted in longer sleep, improved daytime sleep efficiency (SE) and reduced sleep fragmentation (Sasseville et al., 2009). A similar open-label study of attention deficit hyperactivity disorder (ADHD) with insomnia has also demonstrated improved global Pittsburgh Sleep Quality Index scores in the subjects wearing blue wavelength-blocking glasses (Fargason et al., 2013). ...
... A study of the efficacy of blue wavelength light-filtering glasses for insomnia subjects showed significant improvement in sleep quality and mood (as measured by a sleep diary) compared with the use of yellowtinted "control" glasses, with no change in sleep timing measures such as time to bed or wake-time following use (Burkhart & Phelps, 2009). A shiftwork study investigating blue-blocking lenses also showed improvement primarily in sleep quality rather than circadian measures (Sasseville et al., 2009). The results of this study build on these previous findings investigating the use of lightfiltering glasses in sleep disorders. ...
It has been recently discovered that blue wavelengths form the portion of the visible electromagnetic spectrum that most potently regulates circadian rhythm. We investigated the effect of blue light-blocking glasses in subjects with delayed sleep phase disorder (DSPD). This open-label trial was conducted over 4 consecutive weeks. The DSPD patients were instructed to wear blue light-blocking amber glasses from 21:00 p.m. to bedtime, every evening for 2 weeks. To ascertain the outcome of this intervention, we measured dim light melatonin onset (DLMO) and actigraphic sleep data at baseline and after the treatment. Nine consecutive DSPD patients participated in this study. Most subjects could complete the treatment with the exception of one patient who hoped for changing to drug therapy before the treatment was completed. The patients who used amber lens showed an advance of 78 min in DLMO value, although the change was not statistically significant (p = 0.145). Nevertheless, the sleep onset time measured by actigraph was advanced by 132 min after the treatment (p = 0.034). These data suggest that wearing amber lenses may be an effective and safe intervention for the patients with DSPD. These findings also warrant replication in a larger patient cohort with controlled observations.
... 22 Daytime use of the glasses in permanent night-shift workers resulted in longer sleep, better daytime sleep efficiency, and less sleep fragmentation. 23 Analogously, darkness treatment improved sleep and mood in subjects with bipolar disorder. 24,25 This is the first study to examine the chronobiological treatment of blue wavelength-blocking glasses in adults with ADHD insomnia. ...
... 22 Shift-work studies with polarized lenses also showed improvement primarily in quality rather than circadian measures. 23 In reference to the feasibility of the use of these glasses in ADHD subjects, only two thirds of participating subjects were able to complete the study. Prospective subjects were invited to participate in the study and were not heavily vetted for compliance capability. ...
Rachel E Fargason, Taylor Preston, Emily Hammond, Roberta May, Karen L GambleDepartment of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham School of Medicine, Birmingham, AL, USABackground: The aim of this study was to examine a nonmedical treatment alternative to medication in attention deficit hyperactivity disorder (ADHD) insomnia, in which blue wavelength light-blocking glasses are worn during the evening hours to counteract the phase-delaying effect of light. Outcome measures included sleep quality and midsleep time. The capacity of ADHD subjects to comply with treatment using the glasses was assessed.Methods: Daily bedtime, wake-up time, and compliance diaries were used to assess sleep quality and timing during a baseline observation week and a 2-week intervention period. The Pittsburgh Sleep Quality Index (PSQI) was administered following baseline and intervention. The intervention protocol consisted of use of blue wavelength-blocking glasses and a moderate lighting environment during evening hours.Results: Partial and variable compliance were noted, with only 14 of 22 subjects completing the study due to nonadherence with wearing the glasses and diary completion. Despite the minimum 3-hour recommendation, glasses were worn, on average, for 2.4 hours daily. Lighting was reduced for only 58.7% of the evening. Compared with baseline, the intervention resulted in significant improvement in global PSQI scores, PSQI subcomponent scores, and sleep diary measures of morning refreshment after sleep (P = 0.037) and night-time awakenings (P = 0.015). Global PSQI scores fell from 11.15 to 4.54, dropping below the cut-off score of 5 for clinical insomnia. The more phase-delayed subjects, ie, those with an initial midsleep time after 4:15 am, trended towards an earlier midsleep time by 43.2 minutes following the intervention (P = 0.073). Participants reported less anxiety following the intervention (P = 0.048).Conclusions: Despite only partial compliance with intervention instructions, subjects completing the study showed subjectively reduced anxiety and improved sleep quality on multiple measures. The more sleep-delayed subjects trended toward an earlier sleep period following use of the glasses. Blue-blocking glasses are a potential insomnia treatment for more compliant subjects with ADHD insomnia, especially those with prominent sleep delay. Larger studies of blue light-blocking glasses in more phase-delayed groups could reveal significant advances in chronotherapeutics.Keywords: insomnia, attention deficit hyperactivity disorder, circadian rhythm disorders, chronobiological treatment
... Current interventions for SWD focus predominantly on alleviating sleepiness and increasing alertness in re-entraining the circadian rhythm. Most of the available treatments are pharmacological, such as hypnotics used to improve sleep [10,11], stimulants used to improve alertness [12,13], or luminotherapy used with or without dark sunglasses to shift the circadian rhythm at least partially to thereby improve sleep and alertness [14,15]. Other studies have evaluated the effect on the sleep of night workers, of a nap before [16][17][18] or during the night work [19,20]. ...
... First, the range of increases obtained seems to be higher than that reported in other interventions for shift workers. For instance, wearing dark sunglasses has been shown to increase diurnal TST by an average of 25 minutes [15] while luminotherapy has been shown to produce an increase of about 30 minutes for shift workers [51]. Second, in the present study TST increased in a way comparable to what is expected for TST after sleep restriction therapy for day workers. ...
About 30% of Canadian workers are on shift work schedules, and 8% to 32% of them suffer from Shift Work Disorder (SWD). Only a few behavioural treatments exist to treat this population. This study explores the efficacy and feasibility of sleep restriction therapy for insomnia in a group of night shift workers. Six participants (3 women) meeting SWD criteria were recruited. Mean age was 45.7 years old (SD=8.2). A multiple baseline design was used. After baseline, each participant received six to eight weekly treatment sessions. They completed several self reported questionnaires and a daily sleep diary throughout the study. For each sleep period, sleep variables were calculated from the sleep diary. Two participants had a high treatment response and all others participants had a moderate response. Moreover, all participants presented at least two significant clinical improvements. Five participants presented a decreased in both sleepiness scores. The study suggests that sleep restriction therapy is effective, feasible, and reliable. Sleep restriction therapy for insomnia could improve sleep and diminish sleepiness in shift workers suffering from SWD. The present study opens new possibilities of treatment for shift workers that deserve greater attention in the future.
... The literature search yielded 16 papers that described (25-28, 31, 35, 37), and another evaluated glasses that filtered blue light wavelengths (34). Across all interventions, light intensity ranged from 200-10,000 lux, and cumulative exposure times per shift ranged from 10 minutes to 6 hours. ...
... Nurses who exposed themselves to bright light for ten minutes on workday mornings reported significant improvements in quality of night sleep on day shifts compared to non-bright light exposure periods (36). Wearing blue-blocking goggles while commuting improved total sleep time (34) and sleep efficiency (35) in two studies. The two remaining studies found no significant effect of bright light on sleep parameters (24,29). ...
Objectives:
Associations between shift work and chronic disease have been observed, but relatively little is known about how to mitigate these adverse health effects. This critical review aimed to (i) synthesize interventions that have been implemented among shift workers to reduce the chronic health effects of shift work and (ii) provide an overall evaluation of study quality.
Methods:
MeSH terms and keywords were created and used to conduct a rigorous search of MEDLINE, CINAHL, and EMBASE for studies published on or before 13 August 2012. Study quality was assessed using a checklist adapted from Downs & Black.
Results:
Of the 5053 articles retrieved, 44 met the inclusion and exclusion criteria. Over 2354 male and female rotating and permanent night shift workers were included, mostly from the manufacturing, healthcare, and public safety industries. Studies were grouped into four intervention types: (i) shift schedule; (ii) controlled light exposure; (iii) behavioral; and, (iv) pharmacological. Results generally support the benefits of fast-forward rotating shifts; simultaneous use of timed bright light and light-blocking glasses; and physical activity, healthy diet, and health promotion. Mixed results were observed for hypnotics. Study quality varied and numerous deficiencies were identified.
Conclusions:
Except for hypnotics, several types of interventions reviewed had positive overall effects on chronic disease outcomes. There was substantial heterogeneity among studies with respect to study sample, interventions, and outcomes. There is a need for further high-quality, workplace-based prevention research conducted among shift workers.
... The sunlight panel in Figure 4 indicates that red and orange-tinted lenses could protect night workers from circadian-proficient light exposure while maintaining enough visibility to travel home in the morning. A pilot study of eight permanent shift workers wearing orange-tinted blue blockers after a night shift found a mean nightly increase in subjective total sleep time of 32-34 minutes (Sasseville et al. 2009). Considering these data, future studies should examine variations between lens types in regulating melatonin profiles after a night shift. ...
Lenses that filter short-wavelength (“blue”) light are commercially marketed to improve sleep and circadian health. Despite their widespread use, minimal data are available regarding their comparative efficacy in curtailing blue light exposure while maintaining visibility. Fifty commercial lenses were evaluated using five light sources: a blue LED array, a computer tablet display, an incandescent lamp, a fluorescent overhead luminaire, and sunlight. Absolute irradiance was measured at baseline and for each lens across the visual spectrum (380–780 nm), which allowed calculation of percent transmission. Transmission specificity was also calculated to determine whether light transmission was predominantly circadian-proficient (455–560 nm) or non-proficient (380–454 nm and 561–780 nm). Lenses were grouped by tint and metrics were compared between groups. Red-tinted lenses exhibited the lowest transmission of circadian-proficient light, while reflective blue lenses had the highest transmission. Orange-tinted lenses transmitted similar circadian-proficient light as red-tinted lenses but transmitted more non-circadian-proficient light, resulting in higher transmission specificity. Orange-tinted lenses had the highest transmission specificity while limiting biologically active light exposure in ordinary lighting conditions. Glasses incorporating these lenses currently have the greatest potential to support circadian sleep-wake rhythms.
... A study by Rahman et al. (Rahman et al., 2013) also suggests that filtering short-wavelengths may be an approach to reduce sleep disruption and improve performance in rotating-shift workers. Morning use of such glasses in permanent night-shift workers resulted in longer sleep, improved daytime sleep efficiency, and reduced sleep fragmentation (Sasseville, Benhaberou-Brun, Fontaine, Charon, & Hebert, 2009). An interesting study by Figueiro et al. (Figueiro, Sahin, Wood, & Plitnick, 2016) showed that instead of blocking short-wavelength light, using red light improved measures of alertness, and also improved certain types of performance at night without affecting melatonin levels. ...
Background: Since the discovery of ipRGCs (intrinsic photosensitive retinal ganglion cells) in the retina, new research possibilities for studying the effects of light on the regulation of various behavioral and physiological functions that are independent of image formation arose. As ipRGCs are most sensitive to light of short wavelengths (460-480nm), this dissertation focuses on current topics related to the use of blue light, emphasizing its influence on circadi-an rhythms, sleep and cognitive performance and possible applications in clinical and non-clinical settings.
Aims: The first study aimed to explore the effects of 20 minutes of narrow-bandwidth light exposure of different wavelengths on various neuropsychological and neurophysiological parameters of vigilance in healthy volunteers. The objective of the second study was to assess the effect of combining CBT-I (cognitive-behavioral therapy for insomnia) with wearing blue-light blocking glasses 90 minutes before bedtime on subjective and objective sleep pa-rameters and daily symptoms (anxiety, depression, hyperarousal). The third study aimed to examine subjective sleep quality in a population of healthy volunteers and its association with evening and night light exposure to screens of media devices.
Methods: In the first study, twelve healthy volunteers went through 3 sessions of 20 minutes of light exposure of different wavelengths (455, 508, and 629 nm, with an irradiance of 14 μW/cm2), while EEG was recorded (including ERP (event-related potential) P300 and spec-tral characteristics) and behavioral data (subjective sleepiness, reaction time) gathered. In the second study, 30 patients completed a CBT-I group therapy program, with groups randomly assigned to either active (blue-light filtering glasses) condition, or placebo (glasses without filtering properties) condition. Patients were continually monitored by wristwatch actigraphy, kept their sleep diaries, and completed a standard questionnaire battery at admission and after the end of the program. Lastly, 693 participants in total completed an online questionnaire battery consisting of several sleep-related questionnaires: PSQI, FSS, MCTQ, MEQ and add-ed questions assessing the timing and character of the evening and night exposure to electron-ic devices (TV, PC, tablets and phones) and the use of various filters blocking short-wavelength light.
Results: Our analyses showed that the short-wavelength light condition (455nm) in the first study, was found to be the most effective in terms of its alerting effect for the following vari-ables: subjective sleepiness, the latency of P300 response and absolute EEG power in higher beta (24-34 Hz) and gamma (35-50 Hz) range. The second study showed a greater reduction of anxiety symptoms in the active vs. placebo group of patients and significant prolongation of subjective total sleep time in the active group. When pre- and post-treatment results were compared in both groups separately, significant differences were observed for the scores in the depression and hyperarousal scales in the active group only. In the active group, there was also a significant reduction of subjective sleep latency and an increase of subjective total sleep time without a change in objective sleep duration, which was significantly shortened in the placebo group. In the third study, our analyses showed that longer cumulative exposure to screen light in the evening was associated with greater sleep inertia in the morning and longer sleep latency on workdays. Furthermore, exposure to screen light 1.5h before sleep or during night awakenings was also associated with a decreased chance to wake up before the alarm time, larger social jet-lag, more pronounce daytime dysfunction, decreased subjective sleep quality, and more fatigue. A statistical trend for an increase in the duration of sleep on week-days was also found in participants using blue-light filters in the evening hours.
Conclusion: Our results provide valuable insight into the alerting effects of short-wavelength (blue) light. We also show that avoiding blue light in the evening may help reduce the phase-delaying effect of light and facilitate an improvement in sleep parameters and psychiatric symptoms. Altogether, these results may contribute to the development of new lighting or light-filtering systems and may also be applicable for healthy sleep promotion in both the general and clinical populations.
... The sunlight panel in Figure 4 indicates that red and orange-tinted lenses could protect night workers from circadian-proficient light exposure while maintaining enough visibility to travel home in the morning. A pilot study of eight permanent shift workers wearing orange-tinted blue blockers after a night shift found a mean nightly increase in subjective total sleep time of 32-34 minutes (Sasseville et al. 2009). Considering these data, future studies should examine variations between lens types in regulating melatonin profiles after a night shift. ...
Introduction
Blue-blocking glasses are increasingly used as an intervention for jet-lag and other situations where an individual wishes to promote a “dark” signal despite the presence of ambient light. However, most studies on blue-blockers are done under controlled laboratory settings using emissions generated from electric light sources. The present study evaluated the performance of commercially available blue-blockers under daytime sunlight conditions.
Methods
A calibrated spectroradiometer (Ocean Insight), cosine corrector, optic fiber, and software package were used to measure the absolute irradiance (uW/cm^2/nm) available midday in a standardized location that received direct sunlight. Thirty-one commercially available blue-blockers were individually placed in front of the cosine corrector and intensity was measured and analyzed. Each lens was tested for its ability to block visible light, as well as light within the 440-530nm range. Lenses were evaluated individually and grouped by lens type: red-tinted lenses (RTL), orange-tinted lenses (ORL), orange-tinted lenses with blue reflectivity (OBL), brown-tinted lenses (BTL), yellow-tinted lenses (YTL), and clear lenses with blue reflectivity (RBL).
Results
Across the full spectrum, RTL blocked 66% of the light, OTL blocked 60%, OBL blocked 43%, BTL blocked 56%, YTL blocked 28%, and RBL blocked 20%. When the range was restricted to 440-530nm, RTL blocked 99%, OTL blocked 96%, OBL blocked 90%, BTL blocked 66%, YTL blocked 38%, and RBL blocked 17% of the light. Variation across lens types was significant for the full spectrum (one-way ANOVA, p < 0.0001) as well as the 440-530nm range (one-way ANOVA, p < 0.0001). Individual lenses showed variability in performance, though this variability was smaller than the between-group differences.
Conclusion
Under daylight conditions, red and orange lenses (RTL, OTL, and OBL) blocked at least 90% of the light in the 440-530nm range. Notably, RBL lenses restricted the most short-wavelength light as a proportion of the total light blocked. These data suggest that RTL, OTL, and OBL are effective at blocking the most circadian photosensitive components of daylight at the cost of reducing total illumination.
Support (if any)
R01MD011600, R01DA051321
... Previous work of our team has shown that wearing "blue-blockers" (i.e., orange-tinted lens that block 100% of wavelengths shorter than 540 nm) devised to create "circadian darkness" at the end of the night shift is associated with increased sleep duration and sleep efficiency in night workers (Sasseville et al. 2009). Also, we reported that exposing night workers to 66 µW/cm 2 of 500 nm (blue-green) light at the workplace during the night shift coupled with the wearing of blue-blockers in the morning improved sleep and subjective alertness and delayed circadian phase in an amount of about 2 h after 4 days (Sasseville and Hebert 2010). ...
Circadian adaptation to night work usually does not occur in naturalistic conditions, largely due to exposure to low levels of light during the night and light in the morning on the way home. This leads to circadian misalignment, which has documented deleterious effects on sleep and functioning during waking hours. Chronic circadian misalignment is also being increasingly associated with long-term health comorbidities. As the circadian system is mostly sensitive to short wavelengths (i.e., blue light) and less sensitive to long wavelengths (i.e., red light), shaping light exposure in a "wavelength-wise" manner has been proposed to promote partial adaptation to night shifts, and, therefore, alleviate circadian rhythms disruption. This report presents results from two cross-over designed studies that aimed to investigate the effects of three different light conditions on circadian phase, sleepiness, and alertness of police patrol officers on a rotating shift schedule. The first study took place during summer (n = 15) and the second study (n = 25) during winter/early spring. In both studies, all participants went through three conditions composed of four consecutive night shifts: 1) in-car dim blue light exposure during the night shift and wearing of blue-blocking glasses (BBG) in the morning after 05:00 h; 2) in-car red light exposure during the night shift and wearing of BBG in the morning after 05:00 h; 3) a control condition with no intervention. To assess circadian phase position, salivary melatonin was collected hourly the night before and the night after each condition. Sleep was monitored by wrist actigraphy. Also, a 10-min Psychomotor Vigilance-Task was administered at the beginning and end of each night shift and the Karolinska Sleepiness Scale was completed every 2 h during each night shift. In the summer study, no difference was found in alertness and sleepiness between conditions. Participants though exhibited greater (≈3 h) phase delay after four consecutive night shifts in the control condition (in which morning light exposure was expected to prevent phase delay) than after the blue and red conditions (≈2 h) (in which wearing BBG were expected to promote phase delay). In the second study performed during the winter/early spring, a comparable ≈2 h phase delay was found in each of the three conditions, with no difference in alertness and sleepiness between conditions. In conclusion, participants in both studies exhibited modest phase delay across the four night shifts, even during the control conditions. Still, re-entrainment was not fast enough to produce partial circadian adaptation after four night shifts. A greater number of consecutive night shifts may be necessary to produce enough circadian alignment to elicit benefits on sleepiness and alertness in workers driving a motorized vehicle during night shifts. In-car dim blue light exposure combined with the wearing of BBG in the morning did not show the expected benefits on circadian adaptation, sleepiness, and alertness in our studies. Higher levels of light may be warranted when implementing light intervention in a motorized vehicle setting.
... In terms of sleep, support from health professionals is needed to educate and provide recommendations to encourage better sleeping habits. Examples might include: relaxation techniques; techniques and technological solutions to block out or reduce blue light from LED screens, e.g. using blue light filtering eyeglasses [58]; usage of LED free screens [55]. ...
Background
E-sports is becoming increasingly popular; however, participation is not without risks. Certain lifestyle factors associated with gaming may have negative effects on the wellbeing of the players.
Objective
This systematic review of current studies of e-athletes’ health and wellbeing, primarily focused on athletes level of physical activity. This review also aimed to gain insight on potential health promotion and management strategies for e-gamers and e-athletes.
Method
Four online databases (Medline, SCOPUS, Web of Science, and EBSCO) were searched for full-text English articles published between 2010 and April 2020. A total of six articles met the inclusion criteria and were included for review.
Results
From the six studies, five themes were identified: (1) demographics of e-sports; (2) e-athletes’ level of physical activity, compared to World Health Organization (WHO) guidelines; (3) reasons to engage in physical activity; (4) physical training as a part of e-sport training; and (5) degree of sedentary time. Other findings included e-sports injuries reported by participants, broader aspects of health behaviors, along with proposals for multiple disciplinary team approaches to e-athlete management.
Conclusion
Despite the level of sedentary behavior and e-sports related injuries from the reviewed studies, the majority of e-athletes in the studies included met WHO physical activity guidelines with health promotion as primary motivation. Other health behaviors (sleep and diet) are particularly relevant to e-athletes. More research is needed to better understand this population's health-related behavior and habits to better establish their wellbeing and health risks.
... Research has examined neutralizing exposure to blue light with appropriately colored glasses, and the resultant effects on melatonin secretion, quality of sleep, mood, alertness, drowsiness and retinal phototoxicity. Using blue-blocking glasses preserves nocturnal melatonin concentrations after light exposure (Ayaki et al., 2016;Kayumov et al., 2005;van der Lely et al., 2015;Zerbini et al., 2018) and improves slee duration and sleep quality (Ayaki et al., 2016;Rahman et al. 2013;Burkhart et al., 2009;Sasseville et al., 2009;Sasseville and Hebert, 2010), although mixed results have been found by some authors (Lawrenson et al., 2017). As a preventive measure, shift workers have been advised to avoid exposure to light by wearing blue blocking glasses when they return home after a night shift to facilitate their sleep (van der Lely et al., 2015), although this implementation may be difficult in practice. ...
White light-emitting diodes (LEDs) will likely become the most used lighting devices worldwide in the future because of their very low prices over the course of their long lifespans which can be up to several tens of thousands of hours. The expansion of LED use in both urban and domestic lighting has prompted questions regarding their possible health effects, because the light that they provide is potentially high in the harmful blue band (400-500 nm) of the visible light spectrum. Research on the potential effects of LEDs and their blue band on human health has followed three main directions: 1) examining their retinal phototoxicity 2) examining disruption of the internal clock, i.e., an out-of-sync clock, in shift workers and night workers, including the accompanying health issues, most concerningly an increased relative risk of cancer; and 3) examining risky, inappropriate late-night use of smartphones and consoles among children and adolescents. Here, we document the recognized or potential health issues associated with LED lighting together with their underlying mechanisms of action. There is so far no evidence that LED lighting is deleterious to human retina under normal use. However, exposure to artificial light at night is a new source of pollution because it affects the circadian clock. Blue-rich light, including cold white LEDs, should be considered a new endocrine disruptor, because it affects estrogen secretion and has unhealthful consequences in women, as demonstrated to occur via a complex mechanism.
... It was shown that this reduction leads to decrement of performance, subjective vigilance and efficiency, and affects physiological parameters linked to sleepiness and vigilance (van de Werken et al., 2013) as well as attenuation of LED-induced melatonin suppression in the evening and decreased vigilant attention and subjective alertness before bedtime (van der Lely et al., 2015). Blue-blocking glasses used in particular times of the day proved to change circadian measures such as sleep onset (shown in the study on delayed sleep phase disorder patients, Esaki et al., 2016) or sleep time and efficiency (see shift-work studies by Sasseville et al., 2009;Sasseville and Hébert, 2010). A prolonged reduction in short wavelength was introduced by Giménez et al. (2014) in the study on melatonin and sleep patterns. ...
The short wavelength, i.e., blue light, is crucial for non-image forming effects such as entrainment of the circadian system in humans. Moreover, many studies showed that blue light enhances alertness and performance in cognitive tasks. However, most scientific reports in this topic are based on experiments using short exposure to blue or blue-enriched light, and only a few focused on the effects of its reduced transmittance, especially in longer periods. The latter could potentially give insight into understanding if age-related sleep problems and cognitive decline are related to less amount of blue light reaching the retina, as the eyes’ lenses yellow with age. In this study, we investigated the effects of prolonged blocking of blue light on cognitive functioning, in particular—sustained attention and visuospatial working memory, as well as on sleep, and melatonin and cortisol levels. A group of young, healthy participants was randomly allocated to either blue light blocking or control group. Depending on the group, participants wore amber contact lenses, reducing the transmittance of blue light by ∼90% or regular contact lenses for a period of 4 weeks. No changes were observed for measurements related to sleep and sleep–wake rhythm. Dim light melatonin onset, evening levels of melatonin, and morning cortisol answer did not show any significant alterations during blue light (BL) blockade. The significant effects were revealed both for sustained attention and visuospatial memory, i.e., the longer blocking the blue light lasted, the greater decrease in performance observed. Additionally, the follow-up session conducted ∼1 week after taking off the blue-blocking lenses revealed that in case of sustained attention, this detrimental effect of blocking BL is fully reversible. Our findings provide evidence that prolonged reduction of BL exposure directly affects human cognitive functioning regardless of circadian rhythmicity.
... Additionally, training times may not end until early morning (e.g., 1:00 am), and esports athletes may not retire to their sleep quarters until after sunrise. Thus, practicing sleep guidelines similar to shift workers such as incorporating eyeglasses that block blue light after training may help improve sleep disturbance [53]. ...
Esports is a booming global industry and has been officially included in the lead-up to the 2020 Olympics in Tokyo. Given that esports is a cognitive based activity, and sleep is well known to be critical for optimal cognitive functioning, our research group recently proposed that sleep might be an important determinant of esports performance. The focus of the current review was to expand our limited understanding regarding the role of sleep in esports by exploring risk factors for suboptimal sleep and developing an associated intervention framework. More specifically, we aimed to 1) examine how gaming culture and game genre might negatively influence sleep behaviour, 2) describe a conceptual model to explain how sub-optimal sleep occurs in esports, and 3) outline sleep intervention considerations that specifically meet the needs of esports athletes. We conclude that gaming culture and game genre could both impact the sleep behaviour of esports athletes, via cognitive and behavioural mechanisms. Furthermore, adapting Spielman’s three-factor model to esports may provide a useful and easy to understand conceptualisation for sub-optimal sleep in esports. Lastly, sleep interventions for traditional athletes can be suitably modified for esports but must be comprehensive and extend from a theoretically grounded conceptual model.
... Research has examined neutralizing exposure to blue light with appropriately colored glasses, and the resultant effects on melatonin secretion, quality of sleep, mood, alertness, drowsiness and retinal phototoxicity. Using blue-blocking glasses preserves nocturnal melatonin concentrations after light exposure (Ayaki et al., 2016;Kayumov et al., 2005;van der Lely et al., 2015;Zerbini et al., 2018) and improves slee duration and sleep quality (Ayaki et al., 2016;Rahman et al. 2013;Burkhart et al., 2009;Sasseville et al., 2009;Sasseville and Hebert, 2010), although mixed results have been found by some authors (Lawrenson et al., 2017). As a preventive measure, shift workers have been advised to avoid exposure to light by wearing blue blocking glasses when they return home after a night shift to facilitate their sleep (van der Lely et al., 2015), although this implementation may be difficult in practice. ...
... 4 Previous investigations have examined the effects of filters manipulating short-wavelength light on visual performance, [5][6][7][8][9][10][11][12][13] colour vision, 11,[13][14][15] and steady-state and dynamic parameters of pupil size. 16,17 Furthermore, they have received attention in the domain of sleep medicine and chronobiology, where their effects on melatonin suppression, [18][19][20][21][22][23][24][25] circadian rhythms, [26][27][28][29][30] sleep, 6,17,21,25,[29][30][31][32][33] modulation of alertness by light, 34,35 and for use by shift or night workers 36,37 have been investigated. ...
Purpose:
Optical filters and tints manipulating short-wavelength light (sometimes called 'blue-blocking' or 'blue-attenuating' filters) are used in the management of a range of ocular, retinal, neurological and psychiatric disorders. In many cases, the only available quantification of the optical effects of a given optical filter is the spectral transmittance, which specifies the amount of light transmitted as a function of wavelength.
Methods:
We propose a novel physiologically relevant and retinally referenced framework for quantifying the visual and non-visual effects of these filters, incorporating the attenuation of luminance (luminous transmittance), the attenuation of melanopsin activation (melanopsin transmittance), the colour shift, and the reduction of the colour gamut (gamut reduction). Using these criteria, we examined a novel database of spectral transmittance functions of optical filters (n = 121) which were digitally extracted from a variety of sources.
Results:
We find a large diversity in the alteration of visual and non-visual properties. The spectral transmittance properties of the examined filters vary widely, in terms of shapes and cut-off wavelengths. All filters show relatively more melanopsin attenuation than luminance attenuation (lower melanopsin transmittance than luminous transmittance). Across the data set, we find that melanopsin transmittance and luminous transmittance are correlated.
Conclusions:
We suggest that future studies and examinations of the physiological effects of optical filters quantify the visual and non-visual effects of the filters beyond the spectral transmittance, which will eventually aid in developing a mechanistic understanding of how different filters affect physiology. We strongly discourage comparing the downstream effects of different filters on, e.g. sleep or circadian responses, without considering their effects on the retinal stimulus.
... Three studies highlighted the effectiveness of environmental modifications on sleep. [60][61][62] In a study of light supplementation/modification in a group of shift-working nurses, circadian rhythms, as assessed by core body temperature and salivary melatonin, improved. 60 The study employed supplemental bright light during the first 6 hours of their shift, then participants wore darkening goggles at the end of their shift to limit light exposure prior to daytime sleep after work. ...
Study objectives:
The purpose of this review is to synthesize the published literature that addresses employer-initiated interventions to improve the sleep of workers and in turn improve health, productivity, absenteeism, and other outcomes that have been associated with sleep disorders or sleep deficiency.
Methods:
We conducted a systematic search and a selective narrative review of publications in PubMed from 1966 to December 2017. We extracted study characteristics, including the workers' professions, workplace settings and shift work, and workplace interventions focused on worker sleep. Because of the high degree of heterogeneity in design and outcomes, we conducted a narrative review.
Results:
We identified 219 publications. After restriction to publications with studies of workplace interventions that evaluated the outcomes of sleep duration or quality, we focused on 47 articles. An additional 13 articles were accepted in the pearling process. Most studies employed non-randomized or controlled pretest and posttest designs and self-reported measures of sleep. The most common workplace interventions were educational programs stressing sleep hygiene or fatigue management. Other interventions included timed napping before or after work, urging increased daytime activity levels, modifying workplace environmental characteristics such as lighting, and screening, and referral for sleep disorders treatment. Overall, most reports indicated that employer efforts to encourage improved sleep hygiene and healthier habits result in improvements in sleep duration, sleep quality, and self-reported sleepiness complaints.
Conclusions:
These studies suggest employer-sponsored efforts can improve sleep and sleep-related outcomes. The existing evidence, although weak, suggests efforts by employers to encourage better sleep habits and general fitness result in self-reported improvements in sleep-related outcomes, and may be associated with reduced absenteeism and better overall quality of life. Candidate workplace strategies to promote sleep health are provided.
... Prior investigations have also demonstrated that this therapeutic approach has several other beneficial applications. These include improving sleep in individuals with comorbid attention deficit hyperactivity disorder and circadian rhythm sleep disorder, delayed sleep phase type (Fargason et al., 2013), as an adjunctive to antipsychotic treatment to reduce bipolar disorder-related mania (Henriksen et al., 2014), and to improve sleep in night shift workers (Sasseville et al., 2009). Insomnia is a heterogeneous disorder, with various subtypes (e.g. ...
... On the other hand, following a night shift, workers should as much as possible avoid all exposure to light, whether natural or at home, so as to facilitate being able to get to sleep. Glasses that filter out blue light appear to be beneficial in this regard [193][194][195], although this could be difficult to implement in practice. ...
Exposure to Artificial Light At Night (ALAN) results in a disruption of the circadian system, which is deleterious to health. In industrialized countries, 75% of the total workforce is estimated to have been involved in shift work and night work. Epidemiologic studies, mainly of nurses, have revealed an association between sustained night work and a 50–100% higher incidence of breast cancer. The potential and multifactorial mechanisms of the effects include the suppression of melatonin secretion by ALAN, sleep deprivation, and circadian disruption.
... D'autres approches chronobiologiques prometteuses ont été étudiées en laboratoire. Un certain nombre d'études ont montré que diminuer l'intensité lumineuse dans des longueurs d'onde spécifiques à certains moments de la journée, via des filtres optiques (lunettes), pouvait être favorables à la qualité du sommeil et à la vigilance durant le poste de travail (Sasseville et al., 2009 ;Smith et al., 2012 ;Rahman et al., 2013). Toutefois, compte tenu des faibles populations étudiées dans ces études, ces résultats doivent être répliqués avant que les filtres optiques puissent être recommandés. ...
Introduction
L’Anses a été saisie en 2011 pour procéder à une évaluation des risques sanitaires pour les professionnels exposés à des horaires atypiques, notamment ceux soumis à un travail de nuit habituel, qu’il soit régulier ou non. Elle a mis en place un groupe de travail multidisciplinaire pour la réalisation de cette expertise.
Objectifs
L’objectif principal était de statuer sur l’ensemble des effets sanitaires liés au travail de nuit en s’appuyant principalement sur une analyse critique et une synthèse des données publiées dans la littérature.
Méthode
L’expertise s’est appuyée sur un examen approfondi des données obtenues chez l’homme, notamment à partir d’études épidémiologiques et expérimentales publiées principalement depuis 2010. Le niveau de preuve apporté par ces études a été établi pour chacun des effets sanitaires étudiés.
Résultats
Les résultats de l’expertise mettent en évidence : des effets avérés sur la somnolence, la qualité de sommeil et la réduction du temps de sommeil total, ainsi que sur les métabolismes (syndrome métabolique) ; des effets probables sur la santé psychique, les performances cognitives, l’obésité et la prise de poids, le diabète de type 2 et les maladies coronariennes (ischémie coronaire et infarctus du myocarde) ; des effets possibles sur les dyslipidémies, l’hypertension artérielle et les accidents vasculaires cérébraux ischémiques. Le groupe de travail conclut à un effet probable du travail de nuit sur le risque de cancer, notamment à partir des données épidémiologiques sur le cancer du sein et des données mécanistiques. L’expertise souligne les mécanismes physiopathologiques, en particulier la disruption circadienne et les troubles du sommeil qui peuvent expliquer les effets sanitaires à long terme.
Conclusions
Les recommandations générales pour la prévention s’appuient sur trois axes : les modifications du système horaire pour limiter les perturbations circadiennes et du sommeil, et donc les impacts sur la vie professionnelle et personnelle ; les actions sur les conditions de travail et le contenu du travail afin de ne pas amplifier les effets des horaires de nuit et postés ; les actions sur les parcours professionnels et la gestion des ressources humaines afin de maîtriser la durée d’exposition des travailleurs.
... Prodloužení spánku, zvýšení spánkové efektivity, snížení fragmentace spánku a subjektivní zvýšení vigility u zkoumaných osob bylo dosaženo i ve studiích, kde autoři sledovali použití oranžově zabarvených brýlí po ukončení, resp. dvě hodiny před ukončením noční směny (Sasseville a Hébert, 2010), v průběhu které bylo navíc pracoviště vybaveno i jasným osvětlením obohaceným o modrou složku (Sasseville et al., 2009). otázkou je, jestli je blokování modré složky světla efektivní i z dlouhodobého hlediska. ...
Light is considered one of the most important factors influencing circadian system in humans. Synchronizing effects of light depend on the accuracy of timing, intensity, or duration of light stimulus and on its wavelength. Biological clock located in the suprachiasmatic nucleus is set not only by signals from rods and cones but also through an input from retinal ganglion cells. Their melanopsin-based photoreceptive system is especially sensitive to the blue end of light spectrum, with wavelengths of 460-480 nm. This overview of research findings offers insight on current topics related to the use of blue light, emphasising its influence on circadian rhythms, sleep and cognitive performance.
... Prodloužení spánku, zvýšení spánkové efektivity, snížení fragmentace spánku a subjektivní zvýšení vigility u zkoumaných osob bylo dosaženo i ve studiích, kde autoøi sledovali použití oranžovì zabarvených brýlí po ukonèení, resp. dvì hodiny pøed ukonèením noèní smìny (Sasseville a Hébert, 2010), v prùbìhu které bylo navíc pracovištì vybaveno i jasným osvìtlením obohaceným o modrou složku (Sasseville et al., 2009). ...
Light is considered one of the most important factors influencing circadian system in humans. Synchronizing effects of light depend on the accuracy of timing, intensity, or duration of light stimulus and on its wavelength. Biological clock located in the suprachiasmatic nucleus is set not only by signals from rods and cones but also through an input from retinal ganglion cells. Their melanopsin-based photoreceptive system is especially sensitive to the blue end of light spectrum, with wavelengths of 460-480 nm. This overview of research findings offers insight on current topics related to the use of blue light, emphasising its influence on circadian rhythms, sleep and cognitive performance.
... The source, however may often to be several times more powerful to achieve the dosages necessary for these individual therapeutic effects, or the exposure time must be several times longer. This may pose potentially harmful consequences, or not 28 (Sasseville, Benhaberou-Brun, Fontaine, Charon, & Hebert, 2009) 29 (Boivin, Boudreau, & Tremblay, 2012) 30 (Karu, 1988) 31 (Karu, Pyatibrat, Kalendo, & Esenaliev, 1996) 32 (Karu & Kolyakov, 2005) 33 (Hashmi, et al., 2010) 34 (Poyton & Ball, 2011) 3s (Lister, Wright, & Chappell, 2012) 36 (Krawiecki, Cysewska-Sobusiak, Wiczynski, & Odon, 2008) 37 (Jacques, 2013) 38 (Whelan, et al., 2001) 39 (Panhoca, et al., 2015) 40 (Whelan, et al., 2001) 41 (Nawashiro, Wada, Nakai, & Sato, 2012) 42 (Poyton & Ball, 2011) 43 be effective at all; thus, some moderation is needed. There is, however, research specific to white light indicating that it may have a role to play in modulating immune system activity. ...
This thesis proposes both a physical platform and analytical model for implementing phototherapy in the context of architectural space and dynamic user behavior. By doing so, a number of problems across the fields of (1) healthcare innovation, (2) self-tracking or the "quantified self," and (3) interactive architecture would be solved. First, if healthcare systems are to gain greater insight into a number of conditions that are difficult to diagnose or treat, then passive monitoring and treatment methods must be expanded and improved. Second, if self-tracking devices are to become more accurate in monitoring and informing user health, then more contextual information about user positions and activities with reference to space are needed. Third, if interactive architectural systems are to have continuing relevance, then truly novel applications for augmenting the function of spaces must be explored. The development of a so-called "interactive phototherapy" would provide solutions by (1) increasing patient compliance to phototherapy regimens compared to more conventional methods, (2) improving the accuracy of monitoring information relevant to user health, and (3) expanding the functionality of architectural spaces to novel applications. Interactive phototherapy - a user interaction-oriented approach to phototherapy - is developed in three parts. First, we develop the CityHome, a project of the Changing Places group in the MIT Media Laboratory, as a physical platform capable of meeting technical prerequisites for the implementation of interactive phototherapy. Second, we explain a methodology for analyzing interactive phototherapy that is accessible to architectural designers and related practitioners. Third, we apply this methodology to evaluating hypothetical user interaction scenarios that may occur in the CityHome.
... 70,71 Glasses with ambertinted lenses, otherwise known as blue blockers, when worn at night have the ability to completely prevent this phenomenon and could thus provide great benefits to patients at risk of circadian arrhythmia. 72,73 In the absence of controlled studies, it requires some conjecture to connect the dots of this puzzle. However, there is nothing controversial about the importance of circadian rhythms, little doubt that feeding time has a large impact on them, and no downsides (beyond convenience) to daytime feeding. ...
... Eye protection especially important for personnel who may be traveling between work and home in the bright morning sun: melatonin suppression makes it more difficult to get to sleep. In these cases, it is important that they minimize exposure to daylight by wearing blueblocker glasses before the planned sleep period (19,31,128,129), and that their sleeping quarters are blacked out. Nicotine. ...
This book is for shiftwork schedulers and for teams involved in fatigue risk management systems (FRMS) for 24/7 operations. The book covers shift lengths from four to 24 hours, and numbers of crews from one to five. Shift plan examples include 4-, 6-, 8- 12- and 24-hour shift lengths, split-crew plans, a plan for part-time workers, and eight-plus-twelve-hour shift length combination plans. URL http://www.smashwords.com/books/view/352352
... Light exposure measurements were corrected when the police officers of the intervention group were wearing orange-tinted goggles by using a transmission coefficient of 48%. Because our assessment of light exposure did not quantify the spectral composition of the environmental light (irradiance) but measured illuminance (in lux), we propose this transmission estimate by considering 1) an estimated outdoor light spectrum (light color temperature of 5000 K,Figure S2, [38]), 2) the transmission filter of the orange-tinted goggles (Figure S1 and S2) [39], and 3) the luminous function to transform radiant energy into luminous energy [40] (see Methods S1 for details). We validated this estimate experimentally by measuring the environmental illuminance with and without the orange-tinted goggles in Montreal in the morning with a research photometer (IL1400A, International Light, Peabody, MA, USA). ...
Our aim was to investigate how circadian adaptation to night shift work affects psychomotor performance, sleep, subjective alertness and mood, melatonin levels, and heart rate variability (HRV). Fifteen healthy police officers on patrol working rotating shifts participated to a bright light intervention study with 2 participants studied under two conditions. The participants entered the laboratory for 48 h before and after a series of 7 consecutive night shifts in the field. The nighttime and daytime sleep periods were scheduled during the first and second laboratory visit, respectively. The subjects were considered "adapted" to night shifts if their peak salivary melatonin occurred during their daytime sleep period during the second visit. The sleep duration and quality were comparable between laboratory visits in the adapted group, whereas they were reduced during visit 2 in the non-adapted group. Reaction speed was higher at the end of the waking period during the second laboratory visit in the adapted compared to the non-adapted group. Sleep onset latency (SOL) and subjective mood levels were significantly reduced and the LF∶HF ratio during daytime sleep was significantly increased in the non-adapted group compared to the adapted group. Circadian adaptation to night shift work led to better performance, alertness and mood levels, longer daytime sleep, and lower sympathetic dominance during daytime sleep. These results suggest that the degree of circadian adaptation to night shift work is associated to different health indices. Longitudinal studies are required to investigate long-term clinical implications of circadian misalignment to atypical work schedules.
... En partant du paradigme que le pic nocturne de la mélatonine, dont la sécrétion est bloquée par la lumière, est utile au sommeil car elle augmente la propension au sommeil et que la lumière bleue diminue la sécrétion de l'hormone, filtrer cette lumière bleue par des verres optiques appropriés, conduisant à une situation d'obscurité artificielle, devrait entraîner une amélioration des troubles du sommeil, de la vigilance et des performances chez les patients porteurs de ce type de lunettes. Des travaux préliminaires récents sont très prometteurs à cet égard dans le travail posté de nuit [102][103][104] et chez le sujet âgé [105,106]. ...
The internal clock is synchronized by environmental factors. In humans the main factors are the light-dark alternation, the sleep-wake cycle, and social life. Rhythm desynchronization occurs when the clock is no longer in phase (harmony) with the environment, resulting in a phase shift (phase advance or phase delay) which can produce fatigue, sleep disorders and mood disorders. Clock desynchronization is related to a a loss of adaptation between the clock and synchronizers, to an inability of the clock to be entrained, or to a dysfunction of the clock itself Shiftwork and nightwork, transmeridian flights, depressive states and other psychiatric disorders, as well as blindness, aging and intake in some medications and psychoactive agents like alcohol are among the numerous causes of rhythm desynchronization. Melatonin and light exposure are able to control and resynchronize the clock. The phase response curve (PRC) clearly demonstrates that light exposure and/or melatonin administration are able to shift (advance or delay, depending on their timing) and thereby reset the clock.
... Previous research has shown that night shiftworkers suffer from severe sleepiness and fatigue, sleep disturbance, and work-related disease compared with day workers (Åkerstedt et al., 2008a;Härmä, 2006;Paim et al., 2008;Rutenfranz, 1982). A number of countermeasures involving napping (Saito & Sasaki, 1996), bright light (Lowden et al., 2004), exercise (Kubo et al., 2008), caffeine (Walsh et al., 1990), and blue-blocker glasses (Phipps-Nelson et al., 2009;Sasseville et al., 2009) have been proposed to assist night workers. Napping, in particular, has attracted much attention (e.g., Lovato et al., 2009;Signal et al., 2009;Takahashi et al., 2009;Takeyama et al., 2009). ...
Napping is one strategy that may assist night shiftworkers to cope with sleepiness and fatigue. However, one potential disadvantage of napping is that awakening from naps is disturbed by sleep inertia, which has also been found to impair performance and/or mood, transiently. The authors examined the effects of the timing and length of a night-shift nap on sleep inertia in a laboratory setting. Twelve male university students (mean +/- SD: 21.6 +/- 2.8 yrs) participated in this 3-day experiment, during which included a simulated night shift (22:00-08:00 h) and subsequent day (11:30-17:30 h) and night sleep (00:00-07:00 h). The simulated night shift was designed to include one of five (four nap/one no-nap) conditions. The napping conditions differed by their timing and duration: 00:00-01:00 h (Early 60 min; E60), 00:00-02:00 h (Early 120 min; E120), 04:00-05:00 h (Late 60 min; L60), 04:00-06:00 h (Late 120 min; L120). Participants completed all the experimental conditions in a counterbalanced order. Rectal temperature (R(T)) was recorded throughout the simulated shift and polysomnography (PSG) was recorded during the nap period. Immediately before and after each nap, participants were required to complete a visual analogue scale (VAS) to assess sleepiness and a visual vigilance test (VVT). During the simulated night shift, a set of tasks (an English transcription task, a performance test battery, and a break) was repeated hourly, except during the periods of napping. For each nap condition, the VAS and VVT (reaction time [RT]; lapses >5 s) results were analyzed by two-way, repeated-measures analysis of variance (ANOVA) (nap [nap versus no-nap] x time point [pre-nap versus post-nap]). PSG and R(T) data were analyzed with one-way repeated-measures ANOVA. Marginally significant interactions were observed for RTs and lapses in VVT for the L60 nap condition (p = .071 and p = .070, respectively). However, those effect sizes were moderate (partial eta(2) = 0.266, 0.268, respectively). Post hoc analyses showed significantly longer RTs (p < .05) and more lapses (p < .05) following the L60 nap compared with no nap. In contrast, there was no significant difference in sleepiness between the L60, or any of the other nap conditions, and the no-nap condition. Our findings suggest the effect of sleep inertia on VVT performance was profound in the L60 condition, although no significant effects on sleepiness were self-reported by VAS. The dissociation between performance and sleepiness might reflect an unstable state where participants cannot perceive decline in their performance. The present findings are significant in terms of occupational safety; the practical implication is that great care is needed when taking a 1-h nap between 04:00 and 05:00 h on the night shift.
Shift-working railway personnel are highly susceptible to fatigue stemming from poor-quality sleep that can impair the performance of safety-critical functions. Disruption of the 24-h light–dark pattern incident on the retinae appears to play a central role in exacerbating these problems, especially with respect to exposure to light at night and circadian rhythms disruption. This field study tested and demonstrated the effectiveness and acceptability of an intervention (red and blue light combined with white light) to (1) promote circadian alignment, (2) advance the timing of dim light melatonin onset, (3) improve objective and subjective sleep quality, and (4) reduce subjective sleepiness in an operational context compared to a baseline (conventional lighting) condition. The lighting intervention promoted significantly greater synchrony between day-shift participants’ light–dark exposures and rest–activity patterns, but did not significantly advance the timing of dim light melatonin onset. The intervention was also associated with reduced objective sleep disturbances and improved (albeit less robustly) subjective sleep quality, but it only reduced participants’ subjective sleepiness while they were off duty during the day shift. This research demonstrates that lighting interventions can promote circadian alignment and improve sleep quality among railway shift workers and may be translatable to other 24-h industries.
Between 10 and 30% of workers carry out night work at least once a month and 12–13% are working on rotating or regular night shifts. These atypical work schedules cause irregular, fragmented sleep patterns, as well as alertness and performance impairments at night. Atypical work schedules result in circadian misalignment, a state of desynchronization between the endogenous circadian system and the environment. Working at night also produces a state of internal desynchronization between several levels of the circadian system. Circadian adaptation to a night-oriented schedule is a gradual process requiring extended, consistent, and regular exposure to the altered work-rest cycle. There is a high degree of variability in the capacity of individuals to adapt to night schedules and it is estimated only 1 out of 4 workers is able to do so without specific interventions to facilitate circadian phase shifts. As light is the must powerful synchronizer of human circadian rhythms, countermeasures based on strategic light-dark interventions can favor circadian adaptation to atypical work schedules or modulate the secretion of melatonin at night. Melatonin, a hormone secreted by the pineal gland at night can also be administered exogenously to promote sleep in the daytime and shift human circadian rhythms. Most of our knowledge on the resetting and melatonin suppressive effects of light are based on the study of non-shift working populations in highly controlled laboratory conditions. In the field, exogenous melatonin proved useful to extend daytime sleep, although, still today, its resetting effects of shift workers' circadian rhythms remain unclear. The aim of this article is to review the latest scientific evidence on the usefulness of strategic light-dark interventions and on the use of melatonin and melatonin agonists prior to daytime sleep periods in shift working populations.
Background:
Fatigue negatively impacts mineworker health and safety. In this paper, we identify fatigue interventions tested on industrial shiftworkers and explore their effects and the factors that may influence application in an industrial setting such as a mine site.
Methods:
This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. A structured, systematic search of the literature was conducted to identify relevant studies published between 1980 and 2020. Researchers independently conducted article screening and study quality appraisals against pre-established criteria, and then extracted data and conducted a narrative synthesis of the included studies.
Results:
Seven intervention studies, out of 1651 articles initially screened, were retained for narrative synthesis. Four studies tested the alerting effects of bright-light treatment, one evaluated the effectiveness of blue-light blocking glasses at improving daytime sleep quality and nighttime vigilance, and two examined whether sleep hygiene and alertness management trainings improved sleep quality or alertness. There was substantial evidence for the use of bright-light treatments to improve night shiftworker alertness, but insufficient evidence to draw conclusions about the effectiveness of blue-light blocking glasses and sleep hygiene and alertness management trainings due to the small number of studies included. Shiftworkers were mostly male and employed in industrial subsectors such as production and manufacturing, oil and gas, and transportation. No mining-specific intervention studies were identified.
Conclusions:
Future research is needed to identify effective fatigue risk management interventions for the mining industry as well as best practices for implementing these interventions with mineworkers.
Blue-blocking glasses, also known as amber glasses, are plastic glasses that primarily block blue light. Blue-blocking glasses have been studied as a sleep intervention for insomnia, delayed sleep-phase disorder, shift work, jet lag, and nonpathologic sleep improvement. Blue-blocking glasses have also been studied as a treatment for bipolar disorder, major depression, and postpartum depression. Blue-blocking glasses improve sleep by inducing dim-light melatonin onset by reducing activation of intrinsically photosensitive retinal ganglion cells (ipRGCs) which are most sensitive to blue light and are a major input for circadian regulation; their mechanism for mood regulation is unclear but may be similar to that of dark therapy for bipolar disorder where patients are kept in darkness for an extended period every night. A systematic search of the scientific literature identified a total of 29 experimental publications involving evening wear of blue-blocking glasses for sleep or mood disorders. These consisted of 16 randomized controlled trials (RCTs) published in journals with a total of 453 patients, 5 uncontrolled trials, 1 case series, 1 case study, and 6 abstracts from conference proceedings. Only 1 case study and 1 RCT were for acutely manic patients but both found substantial decreases in manic symptoms with the use of blue-blocking glasses; these give preliminary clinical evidence of efficacy that makes blue-blocking glasses a high-yield intervention to study for bipolar disorder. Findings in the 3 publications for major depression and postpartum depression were heterogeneous and conflicting as to their efficacy. Out of the 24 publications focusing on sleep, there was substantial evidence for blue-blocking glasses being a successful intervention for reducing sleep onset latency in patients with sleep disorders, jet lag, or variable shift work schedules. Given the well-established biological mechanism and clinical research showing that blue-blocking glasses are effective for inducing sleep, they are a viable intervention to recommend to patients with insomnia or a delayed sleep phase.
Esports is becoming increasingly professionalized, yet research on performance management is remarkably lacking. The present study aimed to investigate the sleep and mood of professional esports athletes. Participants were 17 professional esports athletes from South Korea (N = 8), Australia (N = 4), and the United States (N = 5) who played first person shooter games (mean age 20 ± 3.5 years, 100% male). All participants wore a wrist-activity monitor for 7–14 days and completed subjective sleep and mood questionnaires. Participants had a median total sleep time of 6.8 h and a sleep efficiency of 86.4% per night. All participants had significantly delayed sleep patterns (median sleep onset 3:43 a.m. and wake time 11:24 a.m.). Participants had a median sleep onset latency of 20.4 min and prolonged wake after sleep onset of 47.9 min. Korean players had significantly higher depression scores compared to the other groups (p < 0.01) and trained longer per day than the Australian or United States teams (13.4 vs. 4.8 vs. 6.1 h, respectively). Depression scores were strongly correlated with number of awakenings, wake after sleep onset, and daily training time (p < 0.05). As the first pilot sleep study in the esports field, this study indicates that esports athletes show delayed sleep patterns and have prolonged wake after sleep onset. These sleep patterns may be associated with mood (depression) and training time. Sleep interventions designed specifically for esports athletes appear warranted.
Shiftwork is a significant risk factor for a host of negative health and safety outcomes, which have been at least partly attributed to disturbances of the circadian timing system. As a result, an entire sub-field of chronobiology has been devoted to developing and evaluating countermeasures for circadian misalignment, sleep disruption, fatigue, and other issues associated with shiftwork. Much of this research takes place under highly controlled laboratory conditions due to the necessity of accurately characterizing individual rhythms, both for intervention design and assessment of efficacy. Applied studies of interventions for shiftworkers are, by their nature, more complicated, often demonstrating less consistent findings. While this, in part, reflects execution under less rigorously controlled conditions, it may also stem from variability in implementation approaches. A systematic review of published studies (through May 2017) of interventions designed to enhance circadian health in shiftworkers was conducted to determine the frequency and quality of the assessment of implementation as well as barriers and enablers to implementation. A search of PubMed, PsychINFO, Web of Science, and CINAHL databases yielded a total of 5368 unique references. After a title and abstract screen, 323 proceeded to full-text review; 68 of those met final criteria for data extraction. Implementation was assessed to some degree in 60.3% of those 68 articles. Where it was assessed, the mean quality score on a scale from 1 to 5 (1 = very little, 3 = moderate, 5 = very in-depth) was 2.56. One or more enablers were identified in just 17 of the 68 studies (25.0%), and barriers in just 18 (26.5%). Implementation of these interventions is a critical but seldom-acknowledged component of their uptake and effectiveness, and we highly recommend that future shiftworker intervention research make an effort to incorporate formalized assessments of implementation and/or hybrid effectiveness-implementation approaches.
Over a quarter of employees in North America and a fifth of those in the European Union do shift work. Working these schedules increases fatigue, sleepiness, and errors at work. In the long term, it may also increase the risk of cardiovascular disease, gastrointestinal problems, and cancer. Some of these consequences may be partly due to circadian misalignment, in which sleep and activity patterns no longer align with one’s circadian rhythms. Previous research has found that controlling light exposure can improve circadian alignment in individuals who work permanent night shifts. However, light-based interventions are rarely tested with rapidly rotating shift schedules, which include more than one type of shift within the same week (e.g., day shifts followed by night shifts). Further, many of the available interventions are seldom used in the workplace and may be less feasible in healthcare environments. In hospitals, the health and safety of both workers and patients can be compromised by increases in fatigue. We thus developed a practical intervention based on circadian and sleep hygiene principles to reduce some of the negative consequences associated with shift work. We then tested this intervention in a feasibility study of 33 nurses working rapidly rotating shifts. The study took place over two separate periods: the control (observation) period and the intervention period. Each period included two to four consecutive night shifts as well as the two days before and after those shifts. Nurses completed daily self-report questionnaires during both periods. During the intervention period, the nurses additionally followed a fatigue reduction plan. The plan involved 40 min of bright light exposure from a portable light box before night shifts, light avoidance using sunglasses after those shifts, and suggestions regarding the ideal times to sleep and nap. Results showed that nurses complied with the large majority of these recommendations. During the intervention period, nurses reported less fatigue, fewer work errors, better and longer sleep, and a more positive mood. Moreover, nurses with a preference for evenings (i.e., later chronotypes) reported the strongest benefits. Though more controlled studies are needed to assess causal mechanisms and long-term effectiveness, these promising results suggest that light-based interventions are feasible and may be effective at reducing fatigue in rapidly rotating shift workers.
We compared the effects of bedroom-intensity light from a standard fluorescent and a blue- (i.e., short-wavelength) depleted LED source on melatonin suppression, alertness, and sleep. Sixteen healthy participants (8 females) completed a 4-day inpatient study. Participants were exposed to blue-depleted circadian-sensitive (C-LED) light and a standard fluorescent light (FL, 4100 K) of equal illuminance (50 lx) for 8 h prior to a fixed bedtime on two separate days in a within-subject, randomized, cross-over design. Each light exposure day was preceded by a dim light (< 3 lx) control at the same time 24 h earlier. Compared to the FL condition, control-adjusted melatonin suppression was significantly reduced. Although subjective sleepiness was not different between the two light conditions, auditory reaction times were significantly slower under C-LED conditions compared to FL 30 min prior to bedtime. EEG-based correlates of alertness corroborated the reduced alertness under C-LED conditions as shown by significantly increased EEG spectral power in the delta-theta (0.5–8.0 Hz) bands under C-LED as compared to FL exposure. There was no significant difference in total sleep time (TST), sleep efficiency (SE%), and slow-wave activity (SWA) between the two conditions. Unlike melatonin suppression and alertness, a significant order effect was observed on all three sleep variables, however. Individuals who received C-LED first and then FL had increased TST, SE% and SWA averaged across both nights compared to individuals who received FL first and then C-LED. These data show that the spectral characteristics of light can be fine-tuned to attenuate non-visual responses to light in humans.
Mood disorders are wide spread with estimates that one in seven of the population are affected at some time in their life (Kessler et al., 2012). Many of those affected with severe depressive disorders have cognitive deficits which may progress to frank neurodegeneration. There are several peripheral markers shown by patients who have cognitive deficits that could represent causative factors and could potentially serve as guides to the prevention or even treatment of neurodegeneration. Circadian rhythm misalignment, immune dysfunction and oxidative stress and circadian rhythm misalignment are key pathologic processes implicated in neurodegeneration and cognitive dysfunction in depressive disorders. Novel treatments targeting these pathways may therefore potentially improve patient outcomes whereby the primary mechanism of action is outside of the monoaminergic system. Moreover, targeting immune dysfunction, oxidative stress and circadian rhythm misalignment (rather than primarily the monoaminergic system) may hold promise for truly disease modifying treatments that may prevent neurodegeneration rather than simply alleviating symptoms with no curative intent. Further research is required to more comprehensively understand the contributions of these pathways to the pathophysiology of depressive disorders to allow for disease modifying treatments to be discovered.
Adverse work schedules increase the risk of accidents, injuries, acute illness and chronically impaired health for workers. As society moves toward providing many services 24 h per day and 7 day per week, the need is increasing for work schedules characterized by shift work, rotating shifts, and early start times. According to the 2004 Current Population Survey, 18 % of full-time workers in the USA spend some portion of their work schedule outside of a 6 a.m. to 6 p.m. time frame (McMenamin, 2007). Extended work hours (more than 8 h per day, or more than 40 h per week) also are increasing steadily (Caruso, Hitchcock, Dick, Russo, & Schmidt, 2004) for a variety of reasons. Some workers elect to take secondary employment to boost their earnings, particularly those with low wages or whose household income has decreased because of a partner’s unemployment. Others choose, or are required to, work extended hours because of shift design (for example, 12-h shifts as a norm). Since the economic downturn that began in late 2008, there has been a trend for employers to use overtime to manage excess demand, which allows them to maintain productivity without hiring new workers (Maher & Aeppel, 2009). In the USA and Canada, employees work 200–300 h more per year than in France, Germany, or Sweden because of an absence of legal minimums for paid vacation days or holidays (Yelin, 2009).
Shift work often results in a misalignment between circadian rhythms and the sleep–wake schedule. This misalignment and its associated sleep disruption can contribute to the development of cardiovascular diseases, gastrointestinal discomfort, metabolic syndrome, cancer, poor performance, and reduced vigilance during night/early morning shifts. Interventions aiming to realign circadian rhythms to displaced sleep–wake schedules are effective countermeasures for shift-work maladaptation. This article focuses on phototherapy and melatonin administration as chronotherapies designed to reestablish a proper entrainment to shifted schedules. The physiological basis of phase-shifting strategies and results from laboratory simulations and shift-work field studies utilizing these interventions are discussed.
Shift work comprises work schedules that extend beyond the typical "nine-to-five" workday, wherein schedules often comprise early work start, compressed work weeks with 12-hour shifts, and night work. According to recent American and European surveys, between 15 and 30% of adult workers are engaged in some type of shift work, with 19% of the European population reportedly working at least 2hours between 22:00 and 05:00. The 2005 International Classification of Sleep Disorders estimates that a shift work sleep disorder can be found in 2-5% of workers. This disorder is characterized by excessive sleepiness and/or sleep disruption for at least one month in relation with the atypical work schedule. Individual tolerance to shift work remains a complex problem that is affected by the number of consecutive work hours and shifts, the rest periods, and the predictability of work schedules. Sleepiness usually occurs during night shifts and is maximal at the end of the night. Impaired vigilance and performance occur around times of increased sleepiness and can seriously compromise workers' health and safety. Indeed, workers suffering from a shift work sleep-wake disorder can fall asleep involuntarily at work or while driving back home after a night shift. Working on atypical shifts has important socioeconomic impacts as it leads to an increased risk of accidents, workers' impairment and danger to public safety, especially at night. The aim of the present review is to review the circadian and sleep-wake disturbances associated with shift work as well as their medical impacts.
The aim of this study was to reassess and compare the usefulness of the National Library of Medicine (NLM)'s Medical Subject Headings® (MeSH) thesaurus for electronic indexing and retrieval of chronobiologic bibliography, after 4 years from a previous study on the same subject (Portaluppi F. 2007114.
Portaluppi , F . 2007. Consistency and accuracy of the medical subject headings thesaurus for electronic indexing and retrieval of chronobiologic references. Chronobiol Int, 24: 1213–1229. [Taylor & Francis Online]View all references. Consistency and accuracy of the medical subject headings thesaurus for electronic indexing and retrieval of chronobiologic references. Chronobiol Int. 24:1213–1229) which demonstrated inconsistent and inaccurate results obtained with existing chronobiologic MeSH terms and suggested the inclusion in the MeSH thesaurus of some common chronobiologic concepts and definitions. A sample set of 219 recent chronobiologic references was downloaded from the MEDLINE®'s database together with all MeSH entries associated with them. The following descriptors of obvious chronobiologic relevance were reanalyzed: “chronobiology”, “chronobiology disorders”, “biological clocks”, “circadian rhythm”, “chronotherapy”, “periodicity”, “seasons”, “sleep disorders, circadian rhythm” and “time factors”. Results were comparable with the previous study that we did 4 years ago. The MeSH terms of obvious chronobiologic significance are still inconsistently and inaccurately retrieving chronobiologic references, while none of the common chronobiologic concepts that we suggested have been included in the MeSH thesaurus, which remains largely incomplete for chronobiologic use.
The aim of the present combined field and laboratory study was to assess circadian entrainment in two groups of police officers working seven consecutive 88.5-h night shifts as part of a rotating schedule. Eight full-time police officers on patrol (mean age±SD: 29.8±6.5 yrs) were provided an intervention consisting of intermittent exposure to wide-spectrum bright light at night, orange-tinted goggles at sunrise, and maintenance of a regular sleepdarkness episode in the day. Orange-tinted goggles have been shown to block the melatonin-suppressing effect of light significantly more than neutral gray density goggles. Nine control group police officers (mean age±SD: 30.3±4.1 yrs) working the same schedule were enrolled. Police officers were studied before, after (in the laboratory), and during (ambulatory) a series of seven consecutive nights. Urine samples were collected at wake time and bedtime throughout the week of night work and during laboratory visits (1×3h) preceding and following the work week to measure urinary 6-sulfatoxymelatonin (UaMT6s) excretion rate. Subjective alertness was assessed at the start, middle, and end of night shifts. A 10-min psychomotor vigilance task was performed at the start and end of each shift. Both laboratory visits consisted of two 8-h sleep episodes based on the prior schedule. Saliva samples were collected 2×h during waking episodes to assay their melatonin content. Subjective alertness (3×h) and performance (1×2h) were assessed during wake periods in the laboratory. A mixed linear model was used to analyze the progression of UaMt6s excreted during daytime sleep episodes at home, as well as psychomotor performance and subjective alertness during night shifts. Two-way analysis of variance (ANOVA) (factors: laboratory visit and group) were used to compare peak salivary melatonin and UaMT6s excretion rate in the laboratory. In both groups of police officers, the excretion rate of UaMT6s at home was higher during daytime sleep episodes at the end compared to the start of the work week (p<.001). This rate increased significantly more in the intervention than control group (p.032). A significant phase delay of salivary melatonin was observed in both groups at the end of study (p.009), although no significant between-group difference was reached. Reaction speed dropped, and subjective alertness decreased throughout the night shift in both groups (p<.001). Reaction speed decreased throughout the work week in the control group (p≤.021), whereas no difference was observed in the intervention group. Median reaction time was increased as of the 5th and 6th nights compared to the 2nd night in controls (p≤.003), whereas it remained stable in the intervention group. These observations indicate better physiological adaptation in the intervention group compared to the controls. (Author correspondence: [email protected]
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The objective of this study was to quantify daytime sleep in night-shift workers with and without an intervention designed to recover the normal relationship between the endogenous circadian pacemaker and the sleepwake cycle. Workers of the treatment group received intermittent exposure to full-spectrum bright light during night shifts and wore dark goggles during the morning commute home. All workers maintained stable 8-h daytime sleepdarkness schedules. The authors found that workers of the treatment group had daytime sleep episodes that lasted 7.1±.1h (mean±SEM) versus 6.6±.2h for workers in the control group (p.04). The increase in total sleep time co-occurred with a larger proportion of the melatonin secretory episode during daytime sleep in workers of the treatment group. The results of this study showed reestablishment of a phase angle that is comparable to that observed on a day-oriented schedule favors longer daytime sleep episodes in night-shift workers. (Author correspondence: [email protected]
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A significant proportion of the workforce in industrialized countries (16%) are employed as shift workers. These workers may be susceptible to shift work disorder (SWD), a circadian rhythm sleep disorder, particularly those who work at night or on early-morning shifts. Shift work disorder remains an underdiagnosed and undertreated problem among this population. Patients with SWD have difficulty initiating sleep and waking up. Often, these patients have excessive sleepiness during their work shift. Shift work disorder has been associated with decreased productivity, impaired safety, diminished quality of life, and adverse effects on health. Several tools have been validated to assess excessive daytime sleepiness and are often used to assess excessive nighttime sleepiness, such as that experienced in patients with SWD, including the Epworth Sleepiness Scale and the Multiple Sleep Latency Test. The criteria for diagnosing SWD as established by the American Academy of Sleep Medicine (AASM) and published in the International Classification of Sleep Disorders-Second Edition (ICSD-2) were most recently updated in 2005 and thus do not contain newer agents approved for use in patients with SWD. The symptoms of SWD can be treated using behavioral, prescription, and nonprescription therapies. Current treatment guidelines suggest nonpharmacologic interventions, such as exercise and exposure to light. In addition, medications that contain melatonin or caffeine may have clinical benefits in some patients with SWD. However, modafinil and armodafinil are approved by the US Food and Drug Administration to improve wakefulness in patients with excessive sleepiness associated with SWD, and recent data suggest a clinical benefit. The use of these therapies can significantly improve sleep, performance, and quality of life for patients with SWD.
Clinical researchers have recently begun to explore differences between psychotherapy outcome studies that focus on efficacy and those that focus on effectiveness. The authors provide concise descriptions of these research models, followed by more extended consideration of the most important conceptual and empirical distinctions between the two. Research on the efficacy/effectiveness distinction is then put into context: The common treatment variables that also influence treatment outcomes are reviewed. Fifty years of research on psychotherapy outcomes are next considered; contemporary research on the efficacy and effectiveness research models is emphasized. A description and evaluation of current efforts to heighten the value of technique-focused research to clinicians follow. The authors conclude by anticipating some promising future directions in this research domain.
The main objectives of this article are to update the ethical standards for the conduct of human and animal biological rhythm research and recommend essential elements for quality chronobiological research information, which should be especially useful for new investigators of the rhythms of life. A secondary objective is to provide for those with an interest in the results of chronobiology investigations, but who might be unfamiliar with the field, an introduction to the basic methods and standards of biological rhythm research and time series data analysis. The journal and its editors endorse compliance of all investigators to the principles of the Declaration of Helsinki of the World Medical Association, which relate to the conduct of ethical research on human beings, and the Guide for the Care and Use of Laboratory Animals of the Institute for Laboratory Animal Research of the National Research Council, which relate to the conduct of ethical research on laboratory and other animals. The editors and the readers of the journal expect the authors of submitted manuscripts to have adhered to the ethical standards dictated by local, national, and international laws and regulations in the conduct of investigations and to be unbiased and accurate in reporting never-before-published research findings. Authors of scientific papers are required to disclose all potential conflicts of interest, particularly when the research is funded in part or in full by the medical and pharmaceutical industry, when the authors are stock-holders of the company that manufactures or markets the products under study, or when the authors are a recent or current paid consultant to the involved company. It is the responsibility of the authors of submitted manuscripts to clearly present sufficient detail about the synchronizer schedule of the studied subjects (i.e., the sleep-wake schedule, ambient light-dark cycle, intensity and spectrum of ambient light exposure, seasons when the research was conducted, shift schedule in studies involving shift work, and menstrual cycle stage in studies involving young women). Rhythm analysis of time series data should be performed with the perspective that rhythms of different periods might be superimposed upon the observed temporal pattern of interest. A variety of different and complementary statistical procedures can be used for rhythm detection. Fitting a mathematical model to the time series data provides a better and more objective analysis of time series data than simple data inspection and narrative description, and if rhythmicity is documented by objective methods, its characterization is required by relevant parameters such as the rhythm's period (tau), MESOR (time series average), amplitude (range of temporal variation), acrophase (time of peak value), and bathyphase (time of trough value). However, the assumptions underlying the time series modeling must be satisfied and applicable in each case, especially the assumption of sinusoidality in the case of cosinor analysis, before it can be accepted as appropriate. An important aspect of the peer review of manuscripts submitted to Chronobiology International entails judgment of the conformity of research protocols and methods to the standards described in this article.
An English language self-assessment Morningness-Eveningness questionnaire is presented and evaluated against individual differences in the circadian vatiation of oral temperature. 48 subjects falling into Morning, Evening and Intermediate type categories regularly took their temperature. Circadian peak time were identified from the smoothed temperature curves of each subject. Results showed that Morning types and a significantly earlier peak time than Evening types and tended to have a higher daytime temperature and lower post peak temperature. The Intermediate type had temperatures between those of the other groups. Although no significant differences in sleep lengths were found between the three types, Morning types retired and arose significantly earlier than Evening types. Whilst these time significatly correlated with peak time, the questionnaire showed a higher peak time correlation. Although sleep habits are an important déterminant of peak time there are other contibutory factors, and these appear to be partly covered by the questionnaire. Although the questionnaire appears to be valid, further evaluation using a wider subject population is required.
A hospital-based survey on shift work, sleep, and accidents was carried out among 635 Massachusetts nurses. In comparison to nurses who worked only day/evening shifts, rotators had more sleep/wake cycle disruption and nodded off more at work. Rotators had twice the odds of nodding off while driving to or from work and twice the odds of a reported accident or error related to sleepiness. Application of circadian principles to the design of hospital work schedules may result in improved health and safety for nurses and patients.
Fourteen male rotating three-shift workers were subjected to 24-h ambulatory polysomnographic recording in connection with morning, afternoon, and night shift work (at home and at work). Total sleep time, stage 2, rapid-eye-movement sleep, and slow-wave sleep (stages 3 + 4) were significantly reduced during sleep in connection with the night and morning shifts. Other visually scored sleep parameters and slow-wave energy (spectral power density integrated across sleep) were not affected. The content of the sleep cycles did not differ between shifts. The sleep before the morning shift was characterized by subjectively increased difficulties of sleep initiation and sleep termination, as well as by insufficient recuperation. The night shift was characterized by increased subjective difficulties of maintaining sleep, but also by increased ease of sleep initiation. It was concluded that both morning and evening shifts interfered with sleep, although no effects of sleep deprivation were found.
It has been suggested that the wearing of band-pass tints may improve the contrast performance in certain ocular conditions. We examined this by measuring grating visual acuity (VA) for targets of various contrasts. The benefits of Corning CPF 511, 527 and 550 lenses, and neutral density (ND) filters were examined with and without the presence of glare. Generally, patients with anterior sector conditions showed improved performance with band-pass filters (not with ND filters). It is suggested that the filter reduces the scatter within the ocular media. People with retinitis pigmentosa or diabetic retinopathy rarely benefited. The CPF 511 most frequently improved VA followed by CPF 527 and 550 respectively. We suggest that a condition of glare is incorporated when assessing suitability with tints.
Working at night results in a misalignment between the sleep-wake cycle and the output of the hypothalamic pacemaker that regulates the circadian rhythms of certain physiologic and behavioral variables. We evaluated whether such physiologic maladaptation to nighttime work could be prevented effectively by a treatment regimen of exposure to bright light during the night and darkness during the day. We assessed the functioning of the circadian pacemaker in five control and five treatment studies in order to assess the extent of adaptation in eight normal young men to a week of night work. In the control studies, on the sixth consecutive night of sedentary work in ordinary light (approximately 150 lux), the mean (+/- SEM) nadir of the endogenous temperature cycle continued to occur during the night (at 3:31 +/- 0:56 hours), indicating a lack of circadian adaptation to the nighttime work schedule. In contrast, the subjects in the treatment studies were exposed to bright light (7000 to 12,000 lux) at night and to nearly complete darkness during the day, and the temperature nadir shifted after four days of treatment to a significantly later, midafternoon hour (14:53 +/- 0:32; P less than 0.0001), indicating a successful circadian adaptation to daytime sleep and nighttime work. There were concomitant shifts in the 24-hour patterns of plasma cortisol concentration, urinary excretion rate, subjective assessment of alertness, and cognitive performance in the treatment studies. These shifts resulted in a significant improvement in both alertness and cognitive performance in the treatment group during the night-shift hours. We conclude that maladaptation of the human circadian system to night work, with its associated decline in alertness, performance, and quality of daytime sleep, can be treated effectively with scheduled exposure to bright light at night and darkness during the day.
The role of the endogenous circadian pacemaker in the timing of the sleep-wake cycle and the regulation of the internal structure of sleep, including REM sleep, EEG slow-wave (0.75-4.5 Hz) and sleep spindle activity (12.75-15.0 Hz) was investigated. Eight men lived in an environment free of time cues for 33-36 d and were scheduled to a 28 hr rest-activity cycle so that sleep episodes (9.33 hr each) occurred at all phases of the endogenous circadian cycle and variations in wakefulness preceding sleep were minimized. The crest of the robust circadian rhythm of REM sleep, which was observed throughout the sleep episode, was positioned shortly after the minimum of the core body temperature rhythm. Furthermore, a sleep-dependent increase of REM sleep was present, which, interacting with the circadian modulation, resulted in highest values of REM sleep when the end of scheduled sleep episodes coincided with habitual wake-time. Slow-wave activity decreased and sleep spindle activity increased in the course of all sleep episodes. Slow-wave activity in non-REM sleep exhibited a low amplitude circadian modulation which did not parallel the circadian rhythm of sleep propensity. Sleep spindle activity showed a marked endogenous circadian rhythm; its crest coincident with the beginning of the habitual sleep episode. Analyses of the (nonadditive) interaction of the circadian and sleep-dependent components of sleep propensity and sleep structure revealed that the phase relation between the sleep-wake cycle and the circadian pacemaker during entrainment promotes the consolidation of sleep and wakefulness and facilitates the transitions between these vigilance states.
Chronic circadian disturbance is thought to cause many of the health and social problems reported by shift workers. In recent years, appropriately timed exposure to bright light and exogenous melatonin have been used to accelerate adaptation to phase shifts of the circadian system. In this study we compared adaptation to night shift in three groups of subjects. The first treatment group received timed exposure to bright light (4-7,000 lux between 2400 and 0400 hours on each of three night shifts). The second treatment group received exogenous melatonin by capsule (2 mg at 0800 hours then 1 mg at 1100 and 1400 hours). The placebo control groups received either dim red light at less than 50 lux or placebo (sucrose) in identical capsules at the same time. Results indicated that all groups shifted significantly from baseline. Using the dim-light melatonin onset as a circadian marker, the bright-light group shifted the furthest, whereas there was no significant difference between the melatonin and placebo groups. Sleep quality as determined by wrist actigraphy was most improved in the light-treatment group, although the melatonin group also showed significant improvements. Cognitive psychomotor performance was most improved in the light-treatment group and the melatonin group again showed little difference from the control group. Although melatonin was unable to increase the amount of the phase shift following transition to night shift, it is likely that the intermediate levels of improvement in sleep reflect the hypothermic effects of melatonin. By lowering core temperature across the sleep period, sleep may be enhanced. This improvement in sleep quality did not produce concomitant improvements in shift performance for the melatonin group. This suggests that the enhanced performance in the light-treatment group may reflect more direct "energizing" effects. On the basis of these results, bright light is clearly superior in its ability ot phase shift the circadian system and thereby improve sleep and performance. However, melatonin may permit shift workers to override the circadian system for short periods and avoid the potential toxicity due to overzealous manipulations of the circadian pacemaker. In rapidly rotating shift schedules, melatonin may be preferable because it would not require workers to reverse the large phase shift induced by light.
We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.
Concern over safety has resulted in legislation by, for example, the Commission of the European Union, to limit the number of hours worked at night. There is, however, no direct evidence that injuries are more frequent at night. We analysed all 4645 injury incidents reported for a year on a rotating three-shift system in a large engineering company where the a-priori accident risk appeared to be constant. The relative risk of sustaining an injury was 1.23 (95% CI 1.14-1.31) higher on the night shift than on the morning shift, which showed the lowest incidence. The type of work (machine versus self-paced) affected the pattern and nature of injuries; for self-paced work the relative risk of more serious injury on the night shift compared with the morning shift was 1.82 (1.30-2.34).
The circadian rhythms of night shift workers do not usually adjust to their unusual work and sleep schedules, reducing their quality of life and producing potentially dangerous health and safety problems. This paper reviews field studies of simulated night work in which shifted light-dark cycles were constructed with artificial bright or medium-intensity light to produce circadian adaptation, ie the shifting of circadian rhythms to align with night work and day sleep schedules. By using these studies we describe fundamental principles of human circadian rhythms relevant to producing circadian adaptation to night shift work at a level designed for the reader with only a basic knowledge of circadian rhythms. These principles should enable the reader to start designing work/sleep-light/dark schedules for producing circadian adaptation in night shift workers. One specific schedule is presented as an example. Finally, we discuss phase-response curves to light and clarify common misconceptions about the production of circadian rhythm phase shifts.
We tested the hypothesis that circadian adaptation to night work is best achieved by combining bright light during the night shift and scheduled sleep in darkness. Fifty-four subjects participated in a shift work simulation of 4 day and 3 night shifts followed by a 38-h constant routine (CR). Subjects received 2,500 lux (Bright Light) or 150 lux (Room Light) during night shifts and were scheduled to sleep (at home in darkened bedrooms) from 0800 to 1600 (Fixed Sleep) or ad libitum (Free Sleep). Dim light melatonin onset (DLMO) was measured before and after the night shifts. Both Fixed Sleep and Bright Light conditions significantly phase delayed DLMO. Treatments combined additively, with light leading to larger phase shifts. Free Sleep subjects who spontaneously adopted consistent sleep schedules adapted better than those who did not. Neither properly timed bright light nor fixed sleep schedules were consistently sufficient to shift the melatonin rhythm completely into the sleep episode. Scheduling of sleep/darkness should play a major role in prescriptions for overcoming shift work-related phase misalignment.
The photopigment in the human eye that transduces light for circadian and neuroendocrine regulation, is unknown. The aim of this study was to establish an action spectrum for light-induced melatonin suppression that could help elucidate the ocular photoreceptor system for regulating the human pineal gland. Subjects (37 females, 35 males, mean age of 24.5 +/- 0.3 years) were healthy and had normal color vision. Full-field, monochromatic light exposures took place between 2:00 and 3:30 A.M. while subjects' pupils were dilated. Blood samples collected before and after light exposures were quantified for melatonin. Each subject was tested with at least seven different irradiances of one wavelength with a minimum of 1 week between each nighttime exposure. Nighttime melatonin suppression tests (n = 627) were completed with wavelengths from 420 to 600 nm. The data were fit to eight univariant, sigmoidal fluence-response curves (R(2) = 0.81-0.95). The action spectrum constructed from these data fit an opsin template (R(2) = 0.91), which identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cell photopigments for vision. The data also suggest that this new photopigment is retinaldehyde based. These findings suggest that there is a novel opsin photopigment in the human eye that mediates circadian photoreception.
The circadian rhythms of shift workers do not usually phase shift to adapt to working at night and sleeping during the day. This misalignment results in a multitude of negative symptoms including poor performance and reduced alertness during night work and poor daytime sleep at home. After an introduction to circadian principles, we discuss the efficacy of appropriately timed bright light exposure (natural and artificial) and exogenous melatonin administration for producing circadian adaptation to night work. Interventions that generate alternative 24h light/dark patterns that facilitate appropriate circadian phase shifting are discussed. Such interventions include minimizing night workers' exposure to the external light/dark cycle, and the use of intermittent and moving patterns of bright light at work. The efficacy of melatonin in phase shifting circadian rhythms in the field is also addressed and compared to that of bright light. We present sleep/light exposure schedules that could produce circadian adaptation in permanent night workers. We conclude this review by discussing the impact of individual differences on possible circadian interventions and issues associated with the use of bright light interventions in the field.
This article describes the characteristics of shift workers and compares stress factors and health behaviours of shift and regular daytime workers. Based on an analysis of people followed over four years, associations between the incidence of chronic conditions and changes in psychological distress levels are explored in relation to working shift.
Data are from the 2000/01 Canadian Community Health Survey, the longitudinal (1994/95, 1996/97 and 1998/99) and cross-sectional (1994/95) components of the National Population Health Survey, and the Survey of Work Arrangements (1991 and 1995).
Cross-tabulations were used to profile shift workers and to compare some of their health behaviours and sources of stress with those of regular daytime workers. Multivariate analyses were used to examine associations between shift work and the incidence of chronic conditions and changes in psychological distress levels over four years, controlling for other potential confounders.
Men who worked an evening, rotating or irregular shift had increased odds of reporting having been diagnosed with a chronic condition over a four-year period. For both sexes, an evening shift was associated with increases in psychological distress levels over two years.
Light can elicit acute physiological and alerting responses in humans, the magnitude of which depends on the timing, intensity, and duration of light exposure. Here, we report that the alerting response of light as well as its effects on thermoregulation and heart rate are also wavelength dependent. Exposure to 2 h of monochromatic light at 460 nm in the late evening induced a significantly greater melatonin suppression than occurred with 550-nm monochromatic light, concomitant with a significantly greater alerting response and increased core body temperature and heart rate ( approximately 2.8 x 10(13) photons/cm(2)/sec for each light treatment). Light diminished the distal-proximal skin temperature gradient, a measure of the degree of vasoconstriction, independent of wavelength. Nonclassical ocular photoreceptors with peak sensitivity around 460 nm have been found to regulate circadian rhythm function as measured by melatonin suppression and phase shifting. Our findings-that the sensitivity of the human alerting response to light and its thermoregulatory sequelae are blue-shifted relative to the three-cone visual photopic system-indicate an additional role for these novel photoreceptors in modifying human alertness, thermophysiology, and heart rate.
Decreases in melatonin production in human and animals are known to be caused by environmental lighting, especially short-wavelength lighting (between 470 and 525 nm). We investigated the novel hypothesis that the use of goggles with selective exclusion of all wavelengths less than 530 nm could prevent the suppression of melatonin in bright-light conditions during a simulated shift-work experiment. Salivary melatonin levels were measured under dim (<5 lux), bright (800 lux), and filtered (800 lux) light at hourly intervals between 2000 and 0800 h in 11 healthy young males and eight females (mean age, 24.7 +/- 4.6 yr). The measurements were performed during three nonconsecutive nights over a 2-wk period. Subjective sleepiness was measured by self-report scales, whereas objective performance was assessed with the Continuous Performance Test. All subjects demonstrated preserved melatonin levels in filtered light similar to their dim-light secretion profile. Unfiltered bright light drastically suppressed melatonin production. Normalization of endogenous melatonin production while wearing goggles did not impair measures of performance, subjective sleepiness, or alertness.
This brief paper reviews the available published literature on shiftwork and safety that allows the relative risk of "accidents" or injuries associated with specific features of shift systems to be estimated. Three main trends in risk are discussed, namely that (i) risk is higher on the night shift, and to a lesser extent the afternoon shift, than on the morning shift, (ii) risk increases over a span of shifts, especially so if they are night shifts, and (iii) risk increases with increasing shift length over eight hours. We discuss that some of these trends are not entirely consistent with predictions derived from considerations of the circadian variations in sleep propensity or rated sleepiness, and consider factors relating to sleep that may underlie the observed trends in risk. Finally, the practical implications of the trends in risk for the design of safer shift systems are discussed.
To assess the wavelength-dependent sensitivity of the acute effects of ocular light exposure on alertness, performance, waking electroencephalogram (EEG), and cortisol.
A between-subjects design was employed to compare the effects of exposure to 460-nm or 555-nm light for 6.5 hours during the biological night.
Intensive Physiological Monitoring Unit, Brigham and Women's Hospital, Boston, MA.
Sixteen healthy adults (8 women; mean age +/- SD = 23.3 +/- 2.4 years).
Subjects were exposed to equal photon densities (2.8 x 10(13) photons x cm(-2) x s(-1)) of either 460-nm (n = 8) or 555-nm (n = 8) monochromatic light for 6.5 hours, 15 minutes after mydriasis.
Subjects underwent continuous EEG/electrooculogram recordings and completed a performance battery every 30 to 60 minutes. As compared with those exposed to 555-nm light, subjects exposed to 460-nm light had significantly lower subjective sleepiness ratings, decreased auditory reaction time, fewer attentional failures, decreased EEG power density in the delta-theta range (0.5-5.5 Hz), and increased EEG power density in the high-alpha range (9.5-10.5 Hz). Light had no direct effect on cortisol.
Short-wavelength sensitivity to the acute alerting effects of light indicates that the visual photopic system is not the primary photoreceptor system mediating these responses to light. The frequency-specific changes in the waking EEG indicate that short-wavelength light is a powerful agent that immediately attenuates the negative effects of both homeostatic sleep pressure and the circadian drive for sleep on alertness, performance, and the ability to sustain attention.
Periodic circadian (24-h) cycles play an important role in daily hormonal and behavioural rhythms. Usually our sleep/wake cycle, temperature and melatonin rhythms are internally synchronized with a stable phase relationship. When there is a desynchrony between the sleep/wake cycle and circadian rhythm, sleep disorders such as advanced and delayed sleep phase syndrome can arise as well as transient chronobiologic disturbances, for example from jet lag and shift work. Appropriately timed bright light is effective in re-timing the circadian rhythm and sleep pattern to a more desired time, ameliorating these disturbances. Other less potent retiming effects may also be obtained from the judicious use of melatonin and exercise.
This study evaluated the effects of bright light and melatonin on adaptation to night work on an oil rig in the North Sea.
Seventeen persons working a schedule of 2 weeks on a 12-hour shift, with the first week on night shift and the second week on day shift (ie, the swing shift schedule) participated. In a randomized controlled crossover design, the shift workers received a placebo, melatonin (3 mg, 1 hour before bedtime), or bright light (30-minute exposure, individually scheduled) during the first 4 days on the night shift and during the first 4 days on the day shift. Subjective and objective measures of sleepiness (Karolinska Sleepiness Scale and a simple serial reaction-time test) and sleep (diary and actigraphy) were recorded.
Subjective measures indicated that melatonin modestly reduced sleepiness at work during the day shift and increased sleep by 15-20 minutes per day. Bright light gave values in between those of melatonin and the placebo, but with few significant results. According to the objective measures, bright light improved sleep to a minor degree during the night shift. Hardly any side-effects were reported.
Melatonin and bright light modestly improved sleep and sleepiness in this field study. In well-controlled simulated nightwork studies, both melatonin and bright light are more effective in alleviating sleepiness and sleep problems. The less effect in this field study may be due to competing or conflicting factors present in real life or to an inoptimal timing and duration of the treatments.
"Permanent" or "fixed" night shifts have been argued to offer a potential benefit over rotating shift systems in that they may serve to maximize circadian adjustment and hence minimize the various health and safety problems associated with night work. For this reason, some authors have argued in favor of permanent shift systems, but their arguments assume at least a substantial, if not complete, adjustment of the circadian clock. They have emphasized the finding that the day sleeps taken between successive night shifts by permanent night workers are rather longer than those of either slowly or rapidly rotating shift workers, but this could simply reflect increased pressure for sleep. The present paper reviews the literature on the adjustment to permanent night work of the circadian rhythm in the secretion of melatonin, which is generally considered to be the best known indicator of the state of the endogenous circadian body clock. Studies of workers in "abnormal" environments, such as oil rigs and remote mining operations, were excluded, as the nature of these unique settings might serve to assist adjustment. The results of the six studies included indicate that only a very small minority (<3%) of permanent night workers evidence "complete"adjustment of their endogenous melatonin rhythm to night work, less than one in four permanent night workers evidence sufficiently "substantial" adjustment to derive any benefit from it, there is no difference between studies conducted in normal or dim lighting, and there is no evidence of gender difference in the adjustment to permanent night work. It is concluded that in normal environments, permanent night-shift systems are unlikely to result in sufficient circadian adjustment in most individuals to benefit health and safety.
Severe subjective and physiological sleepiness occur in night work, afflict almost all individuals and are associated with a performance impairment severe enough to explain night-work accident data. The alertness deficit is caused by the displacement of work to the circadian phase which is least conducive to alert behaviour, by extension of the time spent awake and by the reduction of sleep length (due to circadian interference with sleep). Sleepiness will be extreme when the three causes are operative simultaneously. The three factors may be used quantitatively to predict sleepiness.
This chapter reviews a broad range of factors that, if controlled, might promote adaptation to nightwork, shiftwork, and extended workshifts. Systematic study has begun in four of the areas reported here: work schedule design, napping, bright light stimulation, and drugs. Physical activity, ambient temperature, diet, and individual behaviors have been studied only superficially.
The response of the human circadian pacemaker to light was measured in 45 resetting trials. Each trial consisted of an initial
endogenous circadian phase assessment, a three-cycle stimulus which included 5 hours of bright light per cycle, and a final
phase assessment. The stimulus induced strong (type 0) resetting, with responses highly dependent on the initial circadian
phase of light exposure. The magnitude and direction of the phase shifts were modulated by the timing of exposure to ordinary
room light, previously thought to be undetectable by the human pacemaker. The data indicate that the sensitivity of the human
circadian pacemaker to light is far greater than previously recognized and have important implications for the therapeutic
use of light in the management of disorders of circadian regulation.
Investigated whether the Stanford Sleepiness Scale (SSS), a self-rating scale used to quantify progressive steps in sleepiness, cross-validates with performance on mental tasks and whether the SSS demonstrates changes in sleepiness with sleep loss. 5 undergraduates were given a brief test of memory and the Wilkinson Addition Test in 2 test sessions and the Wilkinson Vigilance Test in 2 other sessions spaced throughout a 16-hr day for 6 days. Ss made SSS ratings every 15 min during their waking activities. On Night 4, Ss underwent all-night sleep deprivation. On all other nights, Ss were allowed only 8 hrs in bed. Mean SSS ratings correlated r = .68 with performance on the Wilkinson tests. Discrete SSS ratings correlated r = .47 with performance on the memory test. Moreover, mean baseline SSS ratings were found to be significantly lower than corresponding ratings of the deprivation period. (PsycINFO Database Record (c) 2005 APA, all rights reserved)
The sleep and performance of 12 male shift workers, operating a discontinuous, weekly alternating, three-shift system, were monitored over the course of one complete shift cycle. Compared with nocturnal sleep, day sleep was shorter in duration and was degraded in quality, and its sleep stages were temporally disrupted. Simple unprepared reaction time and four-choice reaction time were impaired at night, and simple reaction time deteriorated as a function of the number of days into the shift and the time on task. Sleep and performance changes can be primarily attributed to circadian factors; however, the deterioration in performance from night to night and with time on task is probably due to an accumulative sleep deficit. As far as sleep and performance are concerned, the best shift system is probably one having a short rotation cycle, with afternoon shifts or rest days preceding and following the night shift.
In a group of 6 male subjects sleep was displaced to seven different times of day (one displacement condition per week). The subjects were isolated from external time cues (daylight, clocks, noise) and sleep was allowed to terminate spontaneously. The results showed a pronounced time-of-day variation of total sleep time, stage 2, and rapid eye movement (REM) sleep. Maxima occurred after bedtimes at 1900 hr and 2300 hr, while the minima occurred after bedtimes at 0700 hr and 1100 hr. The latter also was the time of maximum propensity to wake up. Slow wave sleep showed a rapid decrease from high initial levels, irrespective of time of day. Ratings of sleepiness showed a highly significant circadian variation peaking between 0500 hr and 0700 hr. The lowest level of sleepiness coincided with the maximum tendency to wake up, and it was suggested that sleep termination may be closely related to the sleepiness/alertness rhythm.
The contribution of the circadian pacemaker and the sleep homeostat to sleep tendency and consolidation was quantified by forced desynchrony of the sleep-wake cycle from the circadian pacemaker in eight men who lived in time-isolation for 33-36 days. Analysis of 175 polygraphically recorded sleep episodes revealed that the circadian pacemaker and the sleep homeostat contribute about equally to sleep consolidation, and that the phase relationship between these oscillatory processes during entrainment to the 24-h day is uniquely timed to facilitate the ability to maintain a consolidated bout of sleep at night and a consolidated bout of wakefulness throughout the day.
Since the first report in unicells, studies across diverse species have demonstrated that light is a powerful synchronizer which resets, in an intensity-dependent manner, endogenous circadian pacemakers. Although it is recognized that bright light (approximately 7,000 to 13,000 lux) is an effective circadian synchronizer in humans, it is widely believed that the human circadian pacemaker is insensitive to ordinary indoor illumination (approximately 50-300 lux). It has been proposed that the relationship between the resetting effect of light and its intensity follows a compressive nonlinear function, such that exposure to lower illuminances still exerts a robust effect. We therefore undertook a series of experiments which support this hypothesis and report here that light of even relatively low intensity (approximately 180 lux) significantly phase-shifts the human circadian pacemaker. Our results clearly demonstrate that humans are much more sensitive to light than initially suspected and support the conclusion that they are not qualitatively different from other mammals in their mechanism of circadian entrainment.