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Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: CAN we reduce morning bright-light duration?
... Shifting circadian rhythms earlier (phase advance) could help adolescents who are struggling to get sufficient sleep on school nights due to late sleep onset. We have used morning bright light and a gradual advance of sleep/dark to advance circadian rhythms in young adults (Burgess et al., 2003;Eastman et al., 2005;Revell et al., 2006;Smith et al., 2009;Crowley and Eastman, 2015). Studies that have thoroughly tested a morning bright light treatment to phase advance the adolescent circadian system, however, are limited. ...
... Past studies have successfully used morning bright light to advance circadian rhythms in adults (Rimmer et al., 2000;Burgess et al., 2003;Eastman et al., 2005;Revell et al., 2006;Paul et al., 2009;Smith et al., 2009;Burke et al., 2013;Crowley and Eastman, 2015), though the duration of light exposure, the number of days of light exposure, and the pattern of light exposure (continuous vs. intermittent) differed among these studies. Furthermore, some studies tested the combination of afternoon melatonin and morning bright light. ...
... Furthermore, some studies tested the combination of afternoon melatonin and morning bright light. Of relevance to the current study, our laboratory tested different durations of morning bright light given over 3 days of a gradually advancing sleep/dark schedule and 0.5 mg of afternoon melatonin to phase advance circadian rhythms in adults aged 18-40 years (Crowley and Eastman, 2015). All groups received afternoon melatonin and a 1 h/day advance of sleep/dark, and only differed by the morning light pattern: four 30-min exposures spread over 3.5 h ("2 h group"), four 15-min exposures spread over 3.25 h ("1-h group"), and one 30-min exposure ("0.5 h group"). ...
Many adolescents fall asleep too late to get enough sleep (8–10 h) on school nights. Morning bright light advances circadian rhythms and could help adolescents fall asleep earlier. Morning bright light treatment before school, however, is difficult to fit into their morning schedule; weekends are more feasible. We examined phase advances in response to morning light treatment delivered over one weekend. Thirty-seven adolescents (16 males; 14.7–18.0 years) who reported short school-night sleep (≤7 h) and late bedtimes (school-nights ≥23:00; weekend/non-school nights ≥24:00) slept as usual at home for ∼2 weeks (“baseline”) and then kept a fixed sleep schedule (baseline school-night bed and wake-up times ±30 min) for ∼1 week before living in the lab for one weekend. Sleep behavior was measured with wrist actigraphy and sleep diary. On Saturday morning, we woke each participant 1 h after his/her midpoint of baseline weekend/non-school night sleep and 1 h earlier on Sunday. They remained in dim room light (∼20 lux) or received 1.5 or 2.5 h of intermittent morning bright light (∼6000 lux) on both mornings. The dim light melatonin onset (DLMO), a phase marker of the circadian timing system, was measured on Friday and Sunday evenings to compute the weekend circadian phase shift. The dim room light and 1.5-h bright light groups advanced the same amount (0.6 ± 0.4 and 0.6 ± 0.5 h). The 2.5-h bright light group advanced 1.0 ± 0.4 h, which was significantly more than the other groups. These data suggest that it is possible to phase advance the circadian clock of adolescents who have late bedtimes and short school-night sleep in one weekend using light that begins shortly after their sleep midpoint.
... Major light-induced shifts in magnitude and direction were not associated with changes in melatonin suppression in one report [17] and this has been confirmed in a very recent publication [84]. Suitably timed administration of exogenous melatonin can partially counter the phase-shifting effects of light [85], but more importantly can act additively with regard to phase shifts, again when correctly timed [86][87][88]. ...
... The combination of hypnotic and chronobiotic properties is in theory ideal for a jet-lag therapy, but to exploit both requires careful timing together with control of light exposure. Optimal effects can be obtained by the use of both light and melatonin to reinforce a phase shift [86][87][88]. ...
... Another strategy is to initiate an advance or delay of the clock pre-flight by timed post-sleep or pre-sleep light treatment, followed by gradually shifting both sleep and light timing as appropriate to the desired adaptation [36,86,87,140,141]. The use of timed melatonin, sleep and light treatment on a shifting schedule pre-flight can also help rapid adaptation [36,86,87,142]. ...
For many years now a treatment mitigating the debilitating effects of jet lag has been sought. Rapid travel across time zones leads, in most people, to temporary symptoms, in particular poor sleep, daytime alertness and poor performance. Mis-timed circadian rhythms are considered to be the main factor underlying jet-lag symptoms, together with the sleep deprivation from long haul flights. Virtually all aspects of physiology are rhythmic, from cells to systems, and circadian rhythms are coordinated by a central pacemaker or clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN adapts slowly to changes in time zone, and peripheral clocks or oscillators adapt at different rates, such that the organism is in a state of desynchrony from the external environment and internally. Light exposure is the main factor controlling the circadian system and needs to be considered together with any pharmacological interventions. This review covers the relatively new chronobiotic drugs, which can hasten adaptation of the circadian system, together with drugs directly affecting alertness and sleep propensity. No current treatment can instantly shift circadian phase to a new time zone; however, adaptation can be hastened. The melatoninergic drugs are promising but larger trials in real-life situations are needed. For short stopovers it is recommended to preserve sleep and alertness without necessarily modifying the circadian system. New research suggests that modification of clock function via genetic manipulation may one day have clinical applications.
... As a result, the balance may have been disturbed and we may have become more nocturnal [31][32][33]. In that case, it would be even more important to strengthen the circadian phase advance effect and to balance against the influence of night light [34][35][36]. Moreover, the sensitivity to light at night may be a major factor in the nocturnal shift of our circadian phase. ...
... The results of the present study suggest that even 1 h of light exposure may show a clear peak of amplitude in the phase advance zone of the PRC. This negative correlation was also seen in a previous study in which melatonin administration was combined with light exposure [34] and is consistent with the results of a previous study on PRCs with 6.7 h of light exposure [16]. In a study using light at night by Watson et al. [30], the time of light exposure varied among individuals, and the individual differences were therefore controlled by using the relative phase shift computed by dividing an individual's observed phase shift by the predicted phase shift according to past studies. ...
Humans have a circadian rhythm for which the period varies among individuals. In the present study, we investigated the amount of natural phase delay of circadian rhythms after spending a day under dim light (Day 1 to Day 2) and the amount of phase advance due to light exposure (8000 lx, 4100 K) the following morning (Day 2 to Day 3). The relationships of the phase shifts with the circadian phase, chronotype and sleep habits were also investigated. Dim light melatonin onset (DLMO) was investigated as a circadian phase marker on each day. In the 27 individuals used for the analysis, DLMO was delayed significantly (−0.24 ± 0.33 h, p < 0.01) from Day 1 to Day 2 and DLMO was advanced significantly (0.18 ± 0.36 h, p < 0.05) from Day 2 to Day 3. There was a significant correlation between phase shifts, with subjects who had a greater phase delay in the dim environment having a greater phase advance by light exposure (r = −0.43, p < 0.05). However, no significant correlations with circadian phase, chronotype or sleep habits were found. These phase shifts may reflect the stability of the phase, but do not account for an individual's chronotype-related indicators.
... However, very few field experiments were conducted to validate whether additional advance light exposure in the real workspace improved assembly-line workers' health and how effective it would be. The previous findings [8][9][10][11][12][13][14][15][16][17][18][19][20][21][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][43][44][45][46]59,61 on the NIF effects of light exposure revealed a quite mixed picture for lighting interventions during daytime working hours. ...
... 28 Morning light exposure can increase arousal 30 and advance bedtime, 5,13 increase sleep efficiency, 31 and even prolong slow-wave activity (SWA) in sleep. 13 Even exposed to light within a short duration (i.e. 30 minutes), workers may have significant alertness response [32][33][34] and circadian phase shift, 35 but longer light exposure may be more effective than stronger light intensity in a shorter time to impact circadian rhythm. 36 A previous laboratory study 37 also reported the time-of-day-dependent effect of bright light exposure on human psychological functions that also related to the circulating melatonin level. ...
Underexposure to daylight in windowless factories puts assembly-line workers at risk of health problems. To investigate whether the advance light exposure in the early morning and during the lunch break benefits workers’ productivity and night-time sleep, a within-subject experiment was conducted in a factory. Four experimental lighting interventions were provided twice a day before work (8:30–9:00 and 12:00–12:30) for consecutive five workdays, covering two light levels (1440 lx vs. 70 lx), each with two correlated colour temperatures (CCTs) (5300 K vs. 3300 K), plus an additional benchmark dark exposure (4 lx). Participants’ subjective alertness and night-time sleep were measured daily, and the chronotype was monitored once a week. Results showed that a higher illuminance was correlated with increased subjective work alertness and higher sleep efficiency, while a lower CCT slightly improved alertness. The subjective work alertness and sleep efficiency under the two advance bright light exposures were higher than those under the dark exposure, and the responses of subjective alertness were more pronounced in the afternoon than those in the morning. Yet, the chronotype had no evident change in different lighting interventions. The present study indicated that the daily advance light exposure before work could have a delayed effect on participants’ alertness and sleep quality.
... Most clinics recommend patients use light therapy for 30-60 min. This duration can phase advance DLMO (Crowley & Eastman, 2015) and is 75 Modifications to CBT-I/BBT-I for patients with circadian rhythm disorders associated with better compliance than a longer duration of light presentation . Typically, the human circadian system can advance by approximately 1 h per day, and bright light can facilitate this advancement (Burgess, Crowley, Gazda, Fogg, & Eastman, 2003;Crowley & Eastman, 2015). ...
... This duration can phase advance DLMO (Crowley & Eastman, 2015) and is 75 Modifications to CBT-I/BBT-I for patients with circadian rhythm disorders associated with better compliance than a longer duration of light presentation . Typically, the human circadian system can advance by approximately 1 h per day, and bright light can facilitate this advancement (Burgess, Crowley, Gazda, Fogg, & Eastman, 2003;Crowley & Eastman, 2015). In our experience, once patients are using the light therapy regularly, 30 min of light exposure can be sufficient to further advance and/or maintain an earlier sleep-wake schedule. ...
Circadian factors are recognized contributors to insomnia symptoms, whether in the context of full-blown circadian rhythm sleep-wake disorders or subthreshold circadian misalignment. While cognitive-behavioral therapy for insomnia (CBT-I) and brief behavioral treatment of insomnia (BBT-I) consider circadian factors, neither fully leverages available assessment options and chronotherapeutic approaches. In this chapter, we draw on the published literature and anecdotal experience in our clinic to offer suggestions on how to enhance CBT-I (or BBT-I) to identify, characterize, and treat individuals with both insomnia and full-blown circadian rhythm sleep-wake disorders or subthreshold circadian misalignment.
... Crowley and Eastman (2015) 16 and Dewan et al. (2011) 20 demonstrated that the greater the exposure time to phototherapy, the greater magnitude the changes in the secretion of melatonin have, being more efficient than to increase the luminous intensity. That reinforces the result from Kirisoglu and Guilleminault (2004) 10 when they found better values for the group from 45 minutes when compared to the group from 20 minutes of exposure to 10,000 lux. ...
... Light therapy was only a driving force of the results since the advances were greater in the intervention groups, but not differently significant between the groups. These investigations find similarities to others that used advanced sleep protocol with rigorous bedtime 13,16,18,23,24 Adelaide, South Australia.; Patients: 49 adolescents (mean age 14.6 ± 1.0 y, 53% males. ...
Delayed sleep-wake phase disorder (DSWPD) is characterized by sleep onset times, beyond the usual schedules and social conveniences, which potentially impacts on health as well as on school and professional performance. The most common treatment for DSWPD is the light administration (light therapy), through light devices, with or without behavioral instructions. Since there is no consensus in the literature about its efficacy and how it should be processed, this study aims to evaluate the light therapy effectiveness in the delayed sleep-wake phase disorder therapeutics. A systematic review was conducted using the MEDLINE/PubMed, Virtual Health Library Brazil, PsycINFO, Web of Science and Scopus databases along with a hand search until September 2020. The included studies presented participants diagnosed with insomnia or DSWPD, over 18-years old, treated only with morning light therapy, mentioning the light intensity (lux) used, and investigations with a control group. Studies reporting individuals with neurological or psychiatric disorders, shift-workers, or evaluating other sleep disorders were excluded. Among the 411 studies identified, five were selected for this review, resulting in a total sample of 140 individuals. Only two studies produced long-term results, showing that the benefits did not persist. In most studies, there were no statistically significant differences in the variables when comparing the intervention group and the control group. However, there were substantial clinical and laboratory advances in the sleep phase using light therapy when comparing phase advances for the same group concerning baseline values of sleep variables.
... Tryptophan (trp) is the basic molecule that can be converted to serotonin and further degraded to melatonin [16]. Advancement of the circadian phase via morning bright light (BL), in combination with afternoon melatonin uptake, recently proved successful [17]. Numerous studies have reported the impact of light exposure on melatonin production and excretion, with an emphasis on its relevance for cognitive and physical performance [18,19]. ...
... A prospective, explorative crossover design with a washout phase of 7 days was implemented. In order to control for natural daylight, all investigations were performed in the winter months (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). On both test days, the participants slept at their homes, woke at 6:00 a.m., collected their first morning urine samples (all participants were instructed how to provide urine samples), and had their habitual breakfast. ...
Background:
Bright light (BL) has been shown to be effective in enhancing both cognitive and physical performances. Alterations in nighttime melatonin levels have also been observed. However, evaluations of light-induced changes in the preceding biochemical processes are absent. Therefore, the impact of a single morning BL exposure on sensorimotor and visuomotor performance, as well as tryptophan (trp) and trp metabolites, was evaluated in this study.
Methods:
In a crossover design, 33 healthy volunteers were randomly exposed to 30 min of < 150 lx at eye level (office light, OL) and 5000 lx at eye level (bright light, BL) of 6500 K in the morning hours. Trp, sulfatoxymelatonin (aMT6s), and kynurenine (kyn) courses over the morning hours were analyzed, and changes in sensori- and visuomotor measures were examined.
Results:
Motoric performance increased in both setups, independent of light intensity. aMT6s and kyn decreased equally under both lighting conditions. Trp levels decreased from a mean (95% confidence interval) of 82.0 (77.2-86.9) to 66.5 (62.5-70.1) in the OL setup only.
Conclusion:
These data suggest that BL in the morning hours has a limited effect on visuo- and sensorimotor performance. Nevertheless, trp degradation pathways in the morning show diverse courses after OL and BL exposure. This suggests that trp courses can potentially be altered by BL exposure.
... An interesting feature of the setting described here is that in addition to the most common on/off illumination regime employed in rodent research labs, it also provides an illumination option consisting of a smooth dark-to-light transition and vice versa realistically mimicking the natural daily cycle paradigm from sunrise to sunset. This illumination option is of particular interest in investigating the specific dynamics of adaptation to the circadian light cycle [16]. Moreover, the setting can use LEDs with different types of white spectra or color light to study the potential effects of the wavelength on circadian adaptation [17,18]. ...
Exposure of experimental rodents to controlled cycles of light, food, and temperature is important when investigating alterations in circadian cycles that profoundly influence health and disease. However, applying such stimuli simultaneously is difficult in practice. Our aim was to design, build, test, and open-source describe a simple device that subjects a conventional mouse cage to independent cycles of physiologically relevant environmental variables. The device is based on a box enclosing the rodent cage to modify the light, feeding, and temperature environments. The device provides temperature-controlled air conditioning (heating or cooling) by a Peltier module and includes programmable feeding and illumination. All functions are set by a user-friendly front panel for independent cycle programming. Bench testing with a model simulating the CO2 production of mice in the cage showed: a) suitable air renewal (by measuring actual ambient CO2), b) controlled realistic illumination at the mouse enclosure (measured by a photometer), c) stable temperature control, and d) correct cycling of light, feeding, and temperature. The cost of all the supplies (retail purchased by e-commerce) was < 300 US$). Detailed technical information is open-source provided, allowing for any user to reliably reproduce or modify the device. This approach can considerably facilitate circadian research since using one of the described low-cost devices for any mouse group with a given light-food-temperature paradigm allows for all the experiments to be performed simultaneously, thereby requiring no changes in the light/temperature of a general-use laboratory.
... 7 In both humans 8 and mice, 6 blue light preferentially altered the expression of clock genes in the SCN, evincing the greater sensitivity of the master clock to the short wavelength part of the spectrum. Conversely, exposure to blue light in the morning phase-advances the dim light melatonin onset rhythm in humans, 9,10 and again, short-wavelength light is most effective. 11 Furthermore, daytime exposure to blue light is required to suppress melatonin secretion and thereby optimize alertness and cognition during daylight hours. ...
Significance:
Exposure to blue light before bedtime is purported to be deleterious to various aspects of human health. In chicks, blue evening light stimulated ocular growth, suggesting a role in myopia development. To further investigate this hypothesis, we asked if brief blue light altered the compensatory responses to hyperopic defocus.
Purpose:
Previous work showed that several hours evening exposure to blue light stimulated ocular growth in chicks, but morning exposure was only effective at a lower illuminance. By contrast, rearing in blue light is inhibited ocular growth in untreated eyes and eyes exposed to form deprivation or defocus. We studied the effects of brief exposures to blue light on the compensation to hyperopic defocus.
Methods:
Chicks wore monocular negative lenses (-10D) starting at age 10d. They were subsequently exposed to blue light (460 nm) for 4 h in the morning or evening for 8-9 days ("dim": 200 lux: morning n = 9, evening n = 11; "bright": 600 lux: morning n = 8, evening n = 20); controls wore lenses in white light (n = 14). Ultrasonography was done on days 1, 5, 8 and 9 for "evening" groups, and days 1, 6 and 8 for "morning". All data are reported as interocular differences (experimental minus fellow eyes). Refractions were measured on the last day.
Results:
For evening exposure, dim blue light enhanced the axial compensation at all times (change in axial length: d6: 465 vs 329 μm/9d, ANOVA P < .001, P = .03; d9: 603 vs 416 μm/9d, ANOVA p < .001; P < .05). Bright blue light had a transient inhibitory effect (day 5: 160 μm vs 329 μm; P < .005). Refractive errors were consistent with axial growth, with "dim" causing more myopia than "bright" (-9.4 D vs -4.7 D; P < .05). Morning blue light had no significant effect.
Conclusions:
We speculate that these findings reflect a complex interaction between illuminance, defocus and time of day.
... Research has shown additive effects of bright light combined with melatonin (45,46) or exercise (37,38). However, no study has combined all three zeitgebers, nor have studies combined these stimuli at the optimal times based on their respective phase-response curves. ...
Misalignment between the environment and one’s circadian system is a common phenomenon (e.g., jet lag) which can have myriad negative effects on physical and mental health, mental and physiological performance, and sleep. Absent any intervention, the circadian system adjusts only 0.5-1.0 h per day to a shifted light-dark and sleep-wake schedule. Bright light facilitates circadian adjustment, but in field studies, bright light is only modestly better than no stimulus. Evidence indicates that exercise and melatonin can be combined with bright light to elicit larger shifts but no study has combined all of these stimuli or administered them at the times that are known to elicit the largest effects on the circadian system. The aims of this study are to compare the effects of different treatments on circadian adjustment to simulated jet lag in a laboratory. Following 2 weeks of home recording, 36 adults will spend 6.5 consecutive days in the laboratory. Following an 8 h period of baseline sleep recording on the participant’s usual sleep schedule on Night 1 (e.g., 0000-0800 h), participants will undergo a 26 h circadian assessment protocol involving 2 h wake intervals in dim light and 1 h of sleep in darkness, repeated throughout the 26 h. During this protocol, all urine voidings will be collected; mood, sleepiness, psychomotor vigilance, and pain sensitivity will be assessed every 3 h, forehead temperature will be assessed every 90 min, and anaerobic performance (Wingate test) will be tested every 6 h. Following, the circadian assessment protocol, the participant’s sleep-wake and light dark schedule will be delayed by 8 h compared with baseline (e.g., 0800-1400 h), analogous to travelling 8 times zones westward. This shifted schedule will be maintained for 3 days. During the 3 days on the delayed schedule, participants will be randomized to one of 3 treatments: (1) Dim Red Light + Placebo Capsules, (2) Bright Light Alone, (3) Bright Light + Exercise + Melatonin. During the final 26 h, all conditions and measures of the baseline circadian protocol will be repeated. Acclimatization will be defined by shifts in circadian rhythms of aMT6s, psychomotor vigilance, Wingate Anaerobic performance, mood, and sleepiness, and less impairments in these measures during the shifted schedule compared with baseline. We posit that Bright Light Alone and Bright Light + Exercise + Melatonin will elicit greater shifts in circadian rhythms and less impairments in sleep, mood, performance, and sleepiness compared with Dim Red Light + Placebo Capsules. We also posit that Bright Light + Exercise + Melatonin will elicit greater shifts and less impairments than Bright Light Alone.
... Experiments first performed in animal models and later in humans showed that exposure to light was a key factor in the circadian system and that light in the morning was linked to awakening, while exposure to light in the dark phase and close to the sleep start time could delay the cycle phase and promote later sleep. These experiments showed that light was an significant synchronizer of circadian rhythms that was capable of modulating the phase of the timing system, promoting earlier or later sleep, in addition to serving as a beacon for the organism expressing its rhythmicity outside the period of 24 hours or irregularly 315 . Reveals, a window of opportunities for the performance of the PT, such as temperature and light itself, being able to research and apply the physical means under the chronobiological optics. ...
This clinical guideline supported by the Brazilian Sleep Association comprises a brief history of the development of Brazilian sleep physiotherapy, outlines the role of the physiotherapist as part of a sleep health team, and describes the clinical guidelines in respect of the management of some sleep disorders by the physiotherapist (including sleep breathing disorders, i.e., obstructive sleep apnea, central sleep apnea, upper airway resistance syndrome, hypoventilation syndromes and overlap syndrome, and pediatric sleep breathing disorders; sleep bruxism; circadian rhythms disturbances; insomnia; and Willis-Ekbom disease/periodic limb movement disorder. This clinical practice guideline reflects the state of the art at the time of publication and will be reviewed and updated as new information becomes available.
... Early morning exposure to light causes a phase advance, which means that melatonin output peaks earlier than it would otherwise. The clocks phase is delayed when the exposure occurs near the end of the afternoon, that is, before the nadir for core body temperature [58]. The impact of light is influenced by its intensity, duration, and spectral qualities. ...
The world has come to a halt as a result of the SARS-CoV-2 pandemic, which has forced most countries to implement lockdown for the maintenance of the spread of infection. This commentary highlights the important role of sleep as a public health problem, especially in stressful life stages such as the COVID-19 pandemic, and is evidence-based and practical for managing sleep disorders during this crisis. People’s routine has changed due to lockdown, including physical activities, eating habits, electronic usage, and sleeping habits. This has caused disruption between the external and internal zeitgebers and have the greatest impact on melatonin hormone. Melatonin is a key regulator of sleep-in body and controls other hormone cycles as endogenous synchroniser. Sleep is influenced by both circadian and homeostatic factors and sleep problems have a wide range of impacts on the body, effecting different physiological system. So, we should maintain a sleep / wake cycle which will benefit the overall health.
... človeško vedenje odvisen od tega, kdaj, kako dolgo smo izpostavljeni svetlobi in kako smo bili izpostavljeni svetlobi v bližnji preteklosti [Wahl, 2019]. Visoka količina svetlobe v jutranjih urah tako premika človekovo uro naprej [Crowley, 2015], čez dan vpliva na razpoloženje ter dviga našo pozornost in produktivnost ( [Figueiro, 2017], [Knoop, 2019], [Sahin, 2014]). Velike količine svetlobe zvečer pa obratno zamikajo cirkadiano uro nazaj ter jo s tem desinhronizirajo s solarnim ciklom [Emens, 2015]. ...
Light, especially daylight, has been recognized by advances in science over the past decades as the main coordinator of the daily biological rhythm of people with a 24-hour solar rhythm. The photoreceptor responsible for the non-visual perception is more sensitive to the blue component of light than the visual perception system. Therefore, it is necessary to evaluate the indoor environment in terms of the spectral composition of light to assess the effects of light on the non-visual system. The purpose of this study was to verify whether the existing tools for multispectral evaluation of the indoor environment are accurate enough to evaluate the non-visual luminous environment. The reliability of the studied tools was tested under clear sky conditions on a north oriented scale model of an office the luminous environment of which was determined experimentally. Experimental results were compared to the simulations evaluated in terms of accuracy and speed. The accuracy of the simulations was evaluated based on the root mean square error (RMSE) of the relative spectral distribution of light (RSPD) and the relative error of the relative melanopic efficiency (RME). The analysis shows that low RMSE of ALFA and Lark tools were achieved when considering RSPD measured outside on the horizontal plane. When evaluating accuracy from the perspective of a hypothetical office user, ALFA adequately simulated the lighting environment with a maximum RMSE = 0.08 and a maximum error in RME = 2.8 %. Lark proves to be less accurate with a maximum RMSE = 0.18 and a maximum error in RME = 16.2 %. Additionally, the ALFA tool proves to be much more time-efficient with more than 20 times shorter simulation runs compared to Lark.Svetlobo, predvsem dnevno svetlobo smo z napredki v znanosti preteklih desetletij prepoznali kot usklajevalec vsakodnev-nega biološkega ritma-cirkadianega ritma ljudi s 24-urnim solarnim ritmom. Vrsta fotoreceptorja, zadolžena za nevizualno zaznavo, je bolj občutljiva za modri del svetlobe kakor sistem vidne zaznave in zato za oceno učinkov svetlobe na nevizualni sistem zahteva sposobnost vrednotenja okolja tudi z vidika spektralne sestave svetlobe. Namen te študije je bil na podlagi opravljenega eksperimenta ocene notranjega okolja pomanjšane pisarne, postavljene na strehi Fakultete za gradbeništvo in geodezijo Univerze v Ljubljani, preveriti, ali so obstoječa orodja večspektralnega vrednotenja notranjega okolja dovolj točna za vrednotenje nevizualnega svetlobnega okolja. Simulacije ovrednotimo z vidika točnosti in hitrosti pri jasnem nebu in severni orientaciji analiziranega prostora. Točnost simulacij ovrednotimo na podlagi korena povprečnega kvadrata napake (RMSE) relativne spektralne porazdelitve svetlobe (RSPD) in relativne napake v relativni melanopski učinkovitosti (RMU). Analiza pokaže nizke RMSE orodij ALFA in Lark, ko obravnavamo RSPD dnevne svetlobe, merjene na horizontalni ravnini zunaj. Kadar točnost vrednotimo z vidika navideznega uporabnika prostora, ALFA vestno simulira svetlobno okolje z največjo RMSE = 0,08 in največjo napako v RMU = 2,8 %. Lark se izkaže za manj natančnega z največjo RMSE = 0,18 in največjo napako v RMU = 16,2 %. Dodatno se izkaže, da je orodje ALFA časovno mnogo učinkovitejše z več kot 20-krat krajšimi simulacijskimi časi v primerjavi z Larkom. Ključne besede: dnevna svetloba, nevizualni učinki svetlobe, spektralne simulacije, pisarna asist. dr. Jaka Potočnik, mag. inž. arh. jaka.potocnik@fgg.uni-lj.si izr. prof. dr. Mitja Košir, univ. dipl. inž. arh.
... Six white and blue light parameters were defined: morning light including recordings during the 2 hours after waking up, evening light including recordings during the 2 hours before going to sleep, and night light including recordings during the hours of sleep. These light parameters were selected as compromises of the 30 minutes to 2 hours in the morning (Corbett et al. 2012;Crowley and Eastman 2015;Geerdink et al. 2016) and 2-4 hours in the evening (Byun et al. 2018;Cajochen et al. 1998;Chang et al. 2015;Green et al. 2017Green et al. , 2018Munch et al. 2011;Obayashi et al. 2014;Rangtell et al. 2016) that has been reported in the literature. In total, 159,657 recordings during the morning, 164,061 during the evening, and 163,223 during the night were included. ...
We aimed to investigate whether higher light intensity in the morning is associated with better nocturnal sleep quality and whether higher light intensities in the evening or night have the opposite effect. Light intensity was recorded for 7 consecutive days across the year among 317 indoor and outdoor daytime workers in Denmark (55–56° N) equipped with a personal light recorder. Participants reported sleep quality after each nocturnal sleep. Sleep quality was measured using three parameters; disturbed sleep index, awakening index, and sleep onset latency. Associations between increasing light intensities and sleep quality were analyzed using mixed effects models with participant identity as a random effect. Overall, neither white nor blue light intensities during morning, evening, or night were associated with sleep quality, awakening, or sleep onset latency of the subsequent nocturnal sleep. However, secondary analyses suggested that artificial light during the morning and day contrary to solar light may increase vulnerability to evening light exposure. Altogether, we were not able to confirm that higher morning light intensity significantly improves self-reported sleep quality or that higher evening or night light intensities impair self-reported sleep quality at exposure levels encountered during daily life in a working population in Denmark. This suggests that light intensities alone are not important for sleep quality to a degree that it is distinguishable from other important parameters in daily life settings.
... Useat käytössä olevat vahtivuorojärjestelmät tasoittuvat lyhyemmissä kuin 24 tunnin jaksoissa ja kiertosuunta on usein taaksepäin, eli seuraavan vuorokauden vahtivuorot alkavat esimerkiksi neljä tuntia aikaisemmin kuin edellisen vuorokauden vuorot (119). Luontaisesti vuorokausirytmiä on kuitenkin helpompi siirtää eteenpäin kuin taaksepäin (120). Singaporen merivoimien henkilöstöllä (n= 24, sotilasarvoja ei kerrottu) tehdyssä pilottitutkimuksessa havaittiin, että vuorokauden pääunijakson pituus oli sekä neljän tunnin taaksepäin kiertävässä että samoihin kellonaikoihin toteutetussa vahtivuorojärjestelmässä hieman alle viisi tuntia. ...
Working in the military has special demands, including 24/7 high performance and flexibility. Commitment to work is high and work is perceived as meaningful, but there are many stressors associated with work. This literature review examines research on peacetime working hours and well-being of officers. Little information was found on the officers´ actual working hours. Self-reported working hours are long, particularly in the United States. There is broadly consistent evidence of sleep deficits among officers in different working contexts. Experiencing severe sleepiness during shifts/flights is also common. There is little research on psychological recovery. The incidence of work stress varies widely between studies. There are particular challenges in balancing work and personal life. Mental health problems and burn out appear to be more common than in the general population. More research data is needed, especially on actual working hours and their association to sleep disorders, recovery and the identification of mental overload. [scoping review in Finnish]
... In one study, subjects took 0.5 mg of melatonin 5 hours before bedtime and received 30 minutes, 1 hour, or 2 hours of intense light (5,000 lux). Subjects exposed to strong light for 2 hours showed the greatest advance in sleep onset time (2.4 hours vs. 1.7 and 1.8 hours for the 30-minutes and 1-hour groups, respectively) [39]. Similarly, in another study, melatonin was administered 5.75 hours before the habitual bedtime, and 3,000 lux of intensive light was given 3 hours before the habitual waking up time, with the results showing that bright light plus melatonin was more effective than either treatment alone [40]. ...
Circadian rhythm sleep–wake disorders (CRSWDs) are a distinct class of sleep disorders caused by alterations to the circadian time-keeping system, its entrainment mechanisms, or a mismatch between the endogenous circadian rhythm and the external environment. The main clinical manifestations are insomnia and excessive daytime sleepiness that often lead to clinically meaningful distress or cause mental, physical, social, occupational, educational, or other functional impairment. CRSWDs are easily mistaken for insomnia or early waking up, resulting in inappropriate treatment. CRSWDs can be roughly divided into two categories, namely, intrinsic CRSWDs, in which sleep disturbances are caused by alterations to the endogenous circadian rhythm system due to chronic changes in the regulation or capture mechanism of the biological clock; and extrinsic circadian rhythm sleep–wake disorders, in which sleep disorders, such as jet lag or shift-work disorder, result from environmental changes that cause a mismatch between sleep–wakefulness times and internal circadian rhythms. Sleep diaries, actigraphy, and determination of day and night phase markers (dim light melatonin onset and core body temperature minimum) have all become routine diagnostic methods for CRSWDs. Common treatments for CRSWD currently include sleep health education, time therapy, light therapy, melatonin, and hypnotic drug therapy. Here, we review the progress in the epidemiology, etiology, diagnostic evaluation, diagnostic criteria, and treatment of intrinsic CRSWD, with emphasis on the latter, in the hope of bolstering the clinical diagnosis and treatment of CRSWDs.
... Many previous studies recognize light environment as one of the most significant factors to solve health problems of shift workers 4,5,11-19 . The bright light of about 900 to 5000 lx is used to reset the circadian phase and promote alertness [20][21][22] . Besides the illumination, the duration and the timing of light exposure are also associated with sleep quality, cognitive performance, and circadian rhythm 12,16,23 . ...
Shift workers are mostly suffered from the disruption of circadian rhythm and health problems. In this study, we designed proper light environment to maintain stable circadian rhythm, cognitive performance, and mood status of shift workers. We used five-channel light-emitting diodes to build up the dynamic daylight-like light environment. The illuminance, correlated color temperature, and circadian action factor of light were tunable in the ranges of 226 to 678 lx, 2680 to 7314 K, and 0.32 to 0.96 throughout the day (5:30 to 19:40). During the nighttime, these parameters maintained about 200 lx, 2700 K, and 0.32, respectively. In this light environment, three subjects had engaged in shift work for 38 consecutive days. We measured plasma melatonin, activity counts, continuous performance tests, and visual analogue scale on mood to assess the rhythm, cognitive performance, and mood of subjects. After 38-day shift work, the subjects’ peak melatonin concentration increased significantly. Their physiological and behavioral rhythms maintained stable. Their cognitive performance improved significantly after night work, compared with that before night work. Their mood status had no significant change during the 38-day shift work. These results indicated that the light environment was beneficial to maintain circadian rhythm, cognitive performance and mood status during long-term shift work in closed environment.
... Sharma's study suggested that a single melatonin injection can entrain the melatonin rhythm [8]. Several light-assisted melatonin intake methods have also been successively verified to be effective [9][10][11]. However, it is still unclear whether taking melatonin for a long time is safe for the human body. ...
Light has been found to affect the circadian clock of the human body. This study aims at exploring the proper light scheme for improving performance and alleviating the negative effects of phase-advance jet lag. Herein, the light intervention intensity during an 8-h working time after a simulated eastward flight is set as a variable. 27 healthy young adults participate in a 7-day circadian phase control and 4-day closed circadian conversion experiment. Participants are assigned to three groups according to lighting conditions: (1) control lighting group (CLG), (2) low-intervention group (LIG), and (3) high-intervention group (HIG). The alertness, sleep quality, and circadian phases of the participants are measured during the closed circadian conversion stage. Statistical analysis results show that, compared to CLG, HIG can effectively reduce the effect of the phase-advance jet lag syndrome on alertness during daytime (p = .028), improve short-term memory task performance (p < .001), and reduce visual fatigue (p = .016); besides, the 8-h light intervention during daytime assists in improving sleep quality. The results for dim light melatonin onset (DLMO) evidence that the HIG scheme can advance the circadian phase by 7.17 ± 0.71 h and is thus recommended for adjusting phase-advance jet lag in interior public workplaces. Finally, a model between light stimulus intensity and the circadian phase shift is deduced with a high correlation R² > 0.99.
... PA benefits musculoskeletal, cognitive [15], cardiometabolic health [16], and sleep [17]. Additionally, exercise outdoors positively influences mental well-being [18] and morning light exposure serves to synchronize the circadian clock [19], restraining our innate tendency to sleep later over successive nights. Even if one does not have time for intentional exercise, walking on the way to and from work contributes significantly to PA [20,21]. ...
Study objectives:
Mobility restrictions imposed to suppress transmission of COVID-19 can alter physical activity (PA) and sleep patterns that are important for health and wellbeing. Characterization of response heterogeneity and their underlying associations may assist in stratifying the health impact of the pandemic.
Methods:
We obtained wearable data covering baseline, incremental mobility restriction and lockdown periods from 1824 city-dwelling, working adults aged 21-40 years, incorporating 206,381 nights of sleep and 334,038 days of PA. Distinct rest-activity rhythm (RAR) profiles were identified using k-means clustering, indicating participants' temporal distribution of step counts over the day. Hierarchical clustering of the proportion of days spent in each of these RAR profiles revealed 4 groups who expressed different mixtures of RAR profiles before and during the lockdown.
Results:
Time in bed increased by 20 min during the lockdown without loss of sleep efficiency, while social jetlag measures decreased by 15 min. Resting heart rate declined ~2 bpm. PA dropped an average of 42%. 4 groups with different compositions of RAR profiles were found. Three were better able to maintain PA and weekday/weekend differentiation during lockdown. The least active group comprising ~51% of the sample, were younger and predominantly singles. Habitually less active already, this group showed the greatest reduction in PA during lockdown with little weekday/weekend differences.
Conclusion:
In the early aftermath of COVID-19 mobility restriction, physical activity appears to be more severely affected than sleep. RAR evaluation uncovered heterogeneity of responses to lockdown that could associate with different outcomes should the resolution of COVID-19 be protracted.
... Bright light above 10,000 lux keeps the circadian rhythm set to awake. Exposure to bright light for more than 30 minutes in the morning will help restore a normal circadian rhythm [68]. On the other hand, when shift work ends, it is also recommended to avoid exposure to bright light by using sunglasses or blue light filters [69]. ...
The “fourth industrial revolution” (FIR) is an age of advanced technology based on information and communication. FIR has a more powerful impact on the economy than in the past. However, the prospects for the labor environment are uncertain. The purpose of this study is to anticipate and prepare for occupational health and safety (OHS) issues.In FIR, nonstandard employment will be common. As a result, it is difficult to receive OHS services and compensation. Excessive trust in new technologies can lead to large-scale or new forms of accidents. Global business networks will cause destruction of workers' biorhythms, some cancers, overwork, and task complexity. The social disconnection because of an independent work will be a risk for worker's mental health. The union bonds will weaken, and it will be difficult to apply standardized OHS regulations to multinational enterprises.To cope with the new OHS issues, we need to establish new concepts of ''decent work” and standardize regulations, which apply to enterprises in each country, develop public health as an OHS service, monitor emerging OHS events and networks among independent workers, and nurture experts who are responsible for new OHS issues. Keywords: Fourth industrial revolution, Occupational health and safety, Workers' compensation, Workers' health
... Bright light has been shown to shift circadian phase depending on time and duration of light administered (phase response curve) [21,22]. Exposure in the early morning phase advances the circadian system causing DLMO to peak earlier and sleep onset to become advanced [23]. Conversely, light exposure during the biological night creates a phase delay shown by a later DLMO [24,25]. ...
Background:
There is conflict between living according to our endogenous biological rhythms and our external environment, with disruptions resulting in negative consequences to health and performance. This is often documented in shift work and jet lag, but 'societal norms' (eg, typical working hours) can create profound issues for 'night owls', people whose internal biological timing predisposes them to follow an unusually late sleep-wake cycle. Night owls have also been associated with health issues, mood disturbances, poorer performance and increased mortality rates.
Methods:
This study used a randomized control trial design aimed to shift the late timing of night owls to an earlier time (phase advance), using non-pharmacological, practical interventions in a real-world setting. These interventions targeted light exposure (through earlier wake up/sleep times), fixed meals times, caffeine intake and exercise.
Results:
Overall, participants demonstrated a significant advance of ∼2 h in sleep/wake timings as measured by actigraphy and circadian phase markers (dim light melatonin onset and peak time of the cortisol awakening response), whilst having no adverse effect on sleep duration. Notably, the phase advance was accompanied by significant improvements to self-reported depression and stress, as well as improved cognitive (reaction time) and physical (grip strength) performance measures during the typical 'suboptimal' morning hours.
Conclusions:
Our findings propose a novel strategy for shifting clock timing towards a pattern that is more aligned to societal demands that could significantly improve elements of performance, mental health and sleep timing in the real world.
... Circadian misalignment through changes in the timing of light exposure and sleep/wake and feeding patterns is likely influential in unhealthy weight gain. Behavioral obesity prevention interventions may focus on promoting consistent sleep timing on both scheduled (e.g., school) and free days, optimal duration of sleep, limiting exposure to artificial light in the evenings [114], encouraging light exposure in the morning [115], encouraging physical activity (to enhance evening fatigue) [116][117][118][119], limiting caffeine intake in the afternoon and evening [120], promoting an overnight fast by limiting food intake in the evening [121], and maintaining consistent meal patterns even on non-school days [121]. ...
... Behavioral obesity prevention interventions targeting at the out of school summer holiday environment may therefore benefit from promoting optimal circadian health during summer by encouraging consistent sleep timing on both scheduled (e.g. school) and free days, optimal duration of sleep, limiting exposure to artificial light in the evenings [115], encouraging light exposure during the day, particularly in the morning [116], encouraging physical activity (to enhance evening fatigue) [99,100,117,118], promoting an overnight fast by limiting food intake in the evening [49], and maintaining consistent meal patterns [49]. It is possible that behavioral changes related to lighting exposure may be more acceptable or easily implemented than recommendations to reduce caloric intake and increase physical activity, thereby increasing rates of intervention adherence. ...
Abstract Children gain weight at an accelerated rate during summer, contributing to increases in the prevalence of overweight and obesity in elementary-school children (i.e., approximately 5 to 11 years old in the US). Int J Behav Nutr Phys Act 14:100, 2017 explained these changes with the “Structured Days Hypothesis” suggesting that environmental changes in structure between the school year and the summer months result in behavioral changes that ultimately lead to accelerated weight gain. The present article explores an alternative explanation, the circadian clock, including the effects of circannual changes and social demands (i.e., social timing resulting from societal demands such as school or work schedules), and implications for seasonal patterns of weight gain. We provide a model for understanding the role circadian and circannual rhythms may play in the development of child obesity, a framework for examining the intersection of behavioral and biological causes of obesity, and encouragement for future research into bio-behavioral causes of obesity in children.
... We found evidence for additive phase-shifting effects of simultaneous bright light and exercise (Youngstedt et al., 2002(Youngstedt et al., , 2016. Other studies have revealed additive effects of bright light and melatonin (Burke et al., 2013;Revell et al., 2006;Crowley & Eastman, 2015). Because the melatonin PRC and the bright light PRC both feature a mid-afternoon peak in phase advance ( Lewy et al., 1998;Burgess et al., 2010;Revell et al., 2012;Crowley & Eastman, 2017), a particularly robust phase advance might be achieved with various combinations of morning bright light and/or exercise and afternoon exercise and/or bright light, and/or melatonin on the same day. ...
Key points:
Exercise elicits circadian phase-shifting effects, but additional information is needed. The phase-response curve describing the magnitude and direction of circadian rhythm phase shifts, depending on the time of the zeigeber (time cue) stimulus, is the most fundamental chronobiological tool for alleviating circadian misalignment and related morbidity. Fifty-one older and 48 young adults followed a circadian rhythms measurement protocol for up to 5.5 days, and performed 1 h of moderate treadmill exercise for 3 consecutive days at one of eight times of the day/night. Temporal changes in the phase of 6-sulphatoxymelatonin (aMT6s) were measured from evening onset, cosine acrophase, morning offset and duration of excretion. Significant phase-response curves were established for aMT6 onset and acrophase with large phase delays from 7:00 pm to 10:00 pm and large phase advances at both 7:00 am and from 1:00 pm to 4:00 pm. Delays or advances would be desired, for example, for adjustment to westward or eastward air travel, respectively. Along with known synergism with bright light, the above PRCs with a second phase advance region (afternoon) could support both practical and clinical applications.
Abstract:
Although bright light is regarded as the primary circadian zeitgeber, its limitations support exploring alternative zeitgebers. Exercise elicits significant circadian phase-shifting effects, but fundamental information regarding these effects is needed. The primary aim of the present study was to establish phase-response curves (PRCs) documenting the size and direction of phase shifts in relation to the circadian time of exercise. Aerobically fit older (n = 51; 59-75 years) and young adults (n = 48; 18-30 years) followed a 90 min laboratory ultrashort sleep-wake cycle (60 min wake/30 min sleep) for up to 5½ days. At the same clock time on three consecutive days, each participant performed 60 min of moderate treadmill exercise (65-75% of heart rate reserve) at one of eight times of day/night. To describe PRCs, phase shifts were measured for the cosine-fitted acrophase of urinary 6-sulphatoxymelatonin (aMT6s), as well as for the evening rise, morning decline and change in duration of aMT6s excretion. Significant PRCs were found for aMT6s acrophase, onset and duration, with peak phase advances corresponding to clock times of 7:00 am and from 1:00 pm to 4:00 pm, delays from 7:00 pm to 10:00 pm, and minimal shifts around 4:00 pm and 2:00 am. There were no significant age or sex differences. The amplitudes of the aMT6s onset and acrophase PRCs are comparable to expectations for bright light of equal duration. The phase advance to afternoon exercise and the exercise-induced PRC for change in aMT6s duration are novel findings. The results support further research exploring additive phase-shifting effects of bright light and exercise and health benefits.
... Circadian misalignment through changes in the timing of light exposure and sleep/wake and feeding patterns is likely influential in unhealthy weight gain. Behavioral obesity prevention interventions may focus on promoting consistent sleep timing on both scheduled (e.g., school) and free days, optimal duration of sleep, limiting exposure to artificial light in the evenings [114], encouraging light exposure in the morning [115], encouraging physical activity (to enhance evening fatigue) [116][117][118][119], limiting caffeine intake in the afternoon and evening [120], promoting an overnight fast by limiting food intake in the evening [121], and maintaining consistent meal patterns even on non-school days [121]. ...
Purpose of Review
The simple energy balance model of obesity is inconsistent with the available findings on obesity etiology, prevention, and treatment. Yet, the most commonly stated causes of pediatric obesity are predicated on this model. A more comprehensive biological model is needed upon which to base behavioral interventions aimed at obesity prevention. In this light, alternative etiologies are little investigated and thereby poorly understood.
Recent Findings
Three candidate alternate etiologies are briefly presented: infectobesity, the gut microbiome, and circadian rhythms.
Summary
Behavioral child obesity preventive investigators need to collaborate with biological colleagues to more intensively analyze the behavioral aspects of these etiologies and to generate innovative procedures for preventing a multi-etiological problem, e.g., group risk analysis, triaging for likely causes of obesity.
... Aschoff suggested that in most instances there are several zeitgebers, that they compete and that regularly one will take the lead and dominate over the others. 2 This has been complemented by Crowley and Eastman 48 and with specific regard to sport by Youngstedt et al 29 showing that rather than one zeitgeber dominating a zeitgeber competition, in many settings there will be zeitgeber interaction 29 48 -be it antagonistic or synergistic. In this vein, we suspect that in some individuals who actively engage in exercise, the zeitgeber effects of exercise may compete-or act antagonistically-against other zeitgebers to the detriment of performance and of chronobiological health. ...
Background
Circadian system time cues (zeitgebers) acting synergistically at the right times can foster chronobiological homeostasis and ultimately health. Modern 24/7 societies are challenging chronobiological homeostasis and public health. Exercise has been discussed as a potential zeitgeber for the human circadian system. Thus, if timed correctly, exercise may help in maintenance of chronobiological homeostasis and foster public health amidst increasingly challenging 24/7 lifestyles.
Objective
To test, using a systematic review of the literature, the following hypothesis: exercise is a zeitgeber for the human circadian system.
Data sources
The PubMed database was systematically searched on 19 October 2017 for relevant scientific studies and reports concerning chronobiology and exercise. Eligibility criteria were defined to include articles considering exercise as a potential zeitgeber for human circadian rhythmicity or chronobiological effects of exercise on health and/or physical performance. Cognitive effects and effects on children were excluded from the synthesis.
Results
Our systematic literature search and synthesis is compatible with the validity of the hypothesis. We report that potential exercise-zeitgeber properties may be used to improve health and performance.
Conclusions
Informed timing of exercise, specific to the circadian rhythm phase and zeitgeber exposure of the individual, must be advocated in performance and disease contexts as an adjunct therapeutic or preventative strategy and physical enhancer.
... The most apparent solution would be to cluster patients with a similar chronotype into the same patient room, to avoid evening/morning disturbances, and to allow later-timed controls or treatments in the night owl chronotype. Treating late chronotype patients with a 30-min morning bright light exposure followed by afternoon melatonin administration could represent an additional solution for advancing the sleep-wake rhythm of late chronotypes [73]. ...
Sleep and circadian disruptions are frequently observed in patients across hospital wards. This is alarming, since impaired nocturnal sleep and disruption of a normal circadian rhythm can compromise health and disturb processes involved in recovery from illness (eg, immune functions). With this in mind, the present narrative review discusses how patient characteristics (sleep disorders, anxiety, stress, chronotype, and disease), hospital routines (pain management, timing of medication, nocturnal vital sign monitoring, and physical inactivity), and hospital environment (light and noise) may all contribute to
sleep disturbances and circadian misalignment in patients. We also propose hospital-based strategies that may help reduce sleep and circadian disruptions in patients admitted to the hospital.
... Because of its potent effect on the circadian system, light therapy devices are used to phase shift circadian rhythmicity to better adapt to night shift work or transmeridian travel (Burgess & Emens, 2016;Crowley & Eastman, 2015). These light therapy devices were initially designed to treat seasonal affective disorder (SAD), for which they are the treatment of choice (Pail et al., 2011). ...
We aimed at assessing whether a head‐mounted light therapy device, enriched in blue wavelengths, suppresses melatonin secretion and improves vigilant attention in the late evening hours. We also assessed whether using such light device is associated with discomfort and physiological stress. Seventeen healthy young participants (eight females) participated in a counterbalanced within‐subject design during which they were exposed for 2 hr before habitual sleep time to a blue‐enriched light (1500 lx) or to a lower intensity red‐light (150 lx) control condition, using a new‐generation light emitting diode (LED) head‐mounted device. Compared to the red light control condition, blue‐enriched light significantly reduced melatonin secretion and reaction times during a psychomotor vigilance task while no significant differences were detected in discomfort and cortisol levels. These results suggest that, compared to a control condition, blue‐enriched light, delivered by a new‐generation head‐mounted device, elicits typical non‐visual responses to light without detectable discomfort and physiological stress. They suggest that such devices might constitute an effective alternative to standard light boxes.
... Because of its potent effect on the circadian system, light therapy devices are used to phase shift circadian rhythmicity to better adapt to night shift work or transmeridian travel (Burgess & Emens, 2016;Crowley & Eastman, 2015). These light therapy devices were initially designed to treat seasonal affective disorder (SAD), for which they are the treatment of choice (Pail et al., 2011). ...
... Saliva samples were collected every 30 mins using Salivettes (Starstedt, Newton, NC, USA). Samples were centrifuged, frozen, and later sent to Solid Phase Inc. (Portland Maine, USA) to be radioimmunoassayed for melatonin [35]. Based on prior work showing that the core body temperature minimum (Tmin) occurs approximately 7 h after the DLMO [36][37][38], Tmin was estimated by adding 7 h to the DLMO for illustration purposes (Fig 2). ...
We conducted two studies of circadian misalignment in non-Hispanic African and European-Americans. In the first, the sleep/wake (light/dark) schedule was advanced 9 h, similar to flying east, and in the second these schedules were delayed 9 h, similar to flying west or sleeping during the day after night work. We confirmed that the free-running circadian period is shorter in African-Americans compared to European-Americans, and found differences in the magnitude and direction of circadian rhythm phase shifts which were related to the circadian period. The sleep and cognitive performance data from the first study (published in this journal) documented the impairment in both ancestry groups due to this extreme circadian misalignment. African-Americans slept less and performed slightly worse during advanced/misaligned days than European-Americans. The current analysis is of sleep and cognitive performance from the second study. Participants were 23 African-Americans and 22 European-Americans (aged 18–44 years). Following four baseline days (8 h time in bed, based on habitual sleep), the sleep/wake schedule was delayed by 9 h for three days. Sleep was monitored using actigraphy. During the last two baseline/aligned days and the first two delayed/misaligned days, beginning 2 h after waking, cognitive performance was assessed every 3 h using the Automated Neuropsychological Assessment Metrics (ANAM) battery. Mixed model ANOVAs assessed the effects of ancestry (African-American or European-American) and condition (baseline/aligned or delayed/misaligned) on sleep and performance. There was decreased sleep and impaired cognitive performance in both ancestry groups during the two delayed/misaligned days relative to baseline/aligned days. Sleep and cognitive performance did not differ between African-Americans and European-Americans during either baseline/aligned or delayed/misaligned days. While our previous work showed that an advance in the sleep/wake schedule impaired the sleep of African-Americans more than European-Americans, delaying the sleep/wake schedule impaired the sleep and cognitive performance of African-Americans and European-Americans equally.
Sleep, one of the foundations of health, is regulated by homeostatic sleep drive and circadian rhythm. Poor sleep has a variety of consequences, and healthcare professionals are particularly susceptible to poor sleep patterns due to stress and time restraints. Sleep health can be improved through diet and a balanced nighttime snack, morning aerobic exercise, nighttime yoga and progressive muscle relaxation meditations, full spectrum light therapy in the mornings, and dietary supplements such as valerian, melatonin, and magnesium, which are shown to improve sleep quality and are safer alternatives to sedative pharmaceuticals. These strategies can be effective in creating better sleep with relatively small changes leading to big differences.
Dental sleep appliances achieve a 50% response in around 65% of patients with obstructive sleep apnea and a complete response in 35–40%. This means that all practitioners will need to augment the effect of a dental sleep appliance at some stage. There are many ways in which adjunctive therapies can be used to augment both the objective and subjective outcomes of DSA therapy. This chapter discusses the use of multiple adjunct therapies including positional therapies, positive airway pressure therapies, therapies aimed at stabilizing or improving compromised anatomy in the upper airway, and therapies aimed at improving the subjective outcomes of sleep.KeywordsDental sleep applianceObstructive sleep apneaPositional obstructive sleep apneaCognitive behavioral therapy for insomniaCircadian rhythm disordersBright light therapyOral EPAPNasal EPAP
Garbellotto, L, Petit, E, Brunet, E, Guirronnet, S, Clolus, Y, Gillet, V, Bourdin, H, and Mougin, F. Gradual advance of sleep-wake schedules before an eastward flight and phase adjustment after flight in elite cross-country mountain bikers: effects on sleep and performance. J Strength Cond Res XX(X): 000-000, 2022-Strategies, for alleviating jet lag, specifically targeted to competitive athletes have never been studied, in ecological conditions. This study aimed to assess the effects of a phase advance before a 7-hour eastward flight followed by a strategy of resynchronization at destination on sleep and physical performance in professional mountain bikers. Six athletes participated in this study divided into 4 periods: (i) baseline (usual sleep-wake rhythm); (ii) phase advance (advance sleep-wake schedules of 3 hours for 6 days); (iii) travel (flight: Paris-Tokyo); and (iv) phase adjustment (resynchronization of sleep-wake schedules). Melatonin pills and light therapy were administrated during the phase advance and phase adjustment. Sleep was recorded by polysomnography and actigraphy, core body temperature (CBT) rhythm was assessed by ingestible capsules, and physical performances were tested by the Wingate and 5-minute maximal exercise tests. Results showed that bedtime was advanced by 2.9 hours at the end of the phase advance (p ≤ 0.01) with a batyphase of CBT advanced by 2.5 hours (p = 0.07). Bedtime was similar at destination compared with baseline. Total sleep time and sleep composition were unchanged at the end of the phase advance or at destination, compared with baseline. Physical performances were maintained after phase advance and at destination. The phase advance enabled to preshift part of the time zones without disturbing sleep and physical performances and contributed to preserving them once at destination. A phase advance before eastward travel represents an effective strategy to counter harmful effects of jet lag.
Nearly all biological processes exhibit circadian rhythms that are generated by circadian clocks in central and peripheral tissues. In mammals a central circadian clock, the suprachiasmatic nucleus helps to align behaviors and physiological processes, including the sleep–wake cycle with the 24-h environment. Disruption of the proper alignment of circadian clocks with the required sleep–wake time leads to development of circadian rhythm sleep–wake disorders. These disorders can develop as a result of pathology at the level of the internal clock, disruption of the ability to receive or process environmental synchronizing signals, or changes to the external environmental time. Treatment of circadian rhythm sleep–wake disorders depends on behavioral adjustments, often in conjunction with specific timing of light and/or melatonin. This chapter will highlight the six primary circadian rhythm sleep–wake disorders, focusing on what is known about their underlying pathogenic mechanisms and the currently recommended treatment strategies.KeywordsCircadianSuprachiasmatic nucleusMelatoninLightActigraphy
Circadian rhythms are endogenous self-sustaining oscillations with a period of approximately 24 hours that impart daily rhythms to physiology and behavior. The circadian clock entrains to the 24-hour day-night cycle through environmental time cues such as light exposure and internal time cues such as melatonin secretion. Circadian rhythmicity is a significant determinant of sleep/wake timing, and disruption to the system and its ability to synchronize to the environment can manifest in circadian rhythm sleep-wake disorders (CRSWDs). The resulting sleep disturbances and circadian misalignment negatively impact quality of life, can interfere with occupational and social obligations, adversely impact mental health, and increase the risk of chronic disease. Due to the rarity of CRSWDs in the general population, patients are commonly misdiagnosed or experience a long delay before being correctly diagnosed. Circadian disorders are also difficult to diagnose as there is often overlap with psychiatric or other comorbid conditions. This chapter aims to provide practical and useful information regarding the CRSWDs to improve diagnosis and management of these disorders.
Introduction
This narrative review summarizes the biology of human circadian rhythms; details the epidemiology, clinical manifestation, and diagnosis of non-24-hour sleep–wake disorder (N24SWD); and reviews the efficacy of possible treatments.
Methods
Searches of targeted phrases, such as “non-24-hour sleep–wake disorder” and “tasimelteon,” were conducted on PubMed between December 2016 and March 2020.
Results
As the world’s population ages, health practitioners frequently work with people who are blind. Damage to the retinal ganglion cells that signal environmental irradiance levels to the suprachiasmatic nucleus prevents many of these individuals from synchronizing their internal clocks to the 24-hour day. As a result, they experience a condition called N24SWD, where the body’s circadian rhythms fall in and out of phase with the solar cycle. The ability to fall asleep and remain asleep is a complex process that depends on many variables, including the release of the neurohormone melatonin. Melatonin is produced at night and is a key regulator of regular sleep cycles. Periods of interrupted sleep, increased sleep latency, and reduced total sleep time occur when melatonin production peaks during daytime. Thus, many persons with N24SWD have difficulty maintaining normal schedules due in part to the mistimed release of melatonin. Randomized clinical trials have shown that melatonin receptor agonist tasimelteon is an effective therapy for individuals with N24SWD. Other treatments have varying efficacy profiles.
Conclusions
Although rare, N24SWD is a serious condition that can impair quality of life for blind persons. Tasimelteon appears to be a safe and efficacious treatment option.
Implications for practitioners
Practitioners can use this information to better understand why blind persons often report difficulties sleeping and to realize that therapeutic options are available to these individuals.
Recent evidence indicates that moderate levels of blue light are sufficient to suppress the nighttime rise in serum melatonin in humans, suggesting that luminous screens may be deleterious to sleep cycles and to other functions. Little is known however, about the effects of exposures to blue light on ocular physiology. We tested the effects of transient blue light exposures of various illuminances on ocular growth rates and ocular rhythms in chicks.
10-day old chicks were exposed to narrow band blue light (460 nm) of specific illuminance for 4 h in the evening (ZT8-ZT12) or the morning (ZT0-ZT4) for 9 days; for the remainder of the day they were in white light (588 lux). For the evening, four illuminances were tested: 0.15 lux; n = 15), 200 lux (radiometrically matched to white controls; n = 16), 600 lux (photometrically matched to white controls; n = 15) or 1000 lux (n = 8). The 600 lux condition was also tested using a 2-hr duration (n = 8). The 200 and 600 lux conditions were extended to 14 and 21 days (n = 8 each). For morning exposures, 200 lux (n = 9), 600 lux (n = 9) and 1000 lux (n = 8) were tested. Controls remained in white light (n = 23). Ocular dimensions were measured by A-scan ultrasonography on days 1 and 9 to assess growth rates. On day 8 or 9, measurements were made at 6-h intervals over 24 h starting at noon to assess rhythm parameters.
Evening exposure to blue light stimulated ocular growth rates relative to controls for all except the bright condition (0.15 lux, 200 lux, 600 lux vs bright and white respectively: 845 μm, 838 μm, 898 μm vs 733 μm and 766 μm; p < 0.05 for all comparisons). 2 hr exposures to 600 lux were similarly effective (915 μm vs 766 μm; p < 0.05). Morning exposures only resulted in growth stimulation for the 200 lux condition (200 lux vs white: 884 μm vs 766 μm; p < 0.05). Furthermore, for this group only, growth of the anterior chamber had a significant contribution to the overall effect (vs white: p < 0.05), and choroids showed significant thickening. For evening exposures to 200 and 600 lux, the growth stimulatory effect lasted for 14 days (p = 0.01); by 21 days only the 600 lux cohort still differed (p < 0.0001). Evening exposures caused circadian disruptions in the choroidal thickness rhythms, and morning exposures disrupted both axial and choroidal rhythms.
Exposure to 4 h of blue light at lower illuminances (less than 1000 lux) at transition times of lights-on and lights-off stimulates ocular growth rates and affects ocular rhythms in chicks, suggesting that such exposures may be deleterious to emmetropization in children.
Internationally, it is said that the “era of sleeping difficulty” has arrived, and for Japanese children, this is no exception. On the other hand, it is well-established that daytime light reception promotes phase advances in melatonin secretion. Thus, it is undeniable that the sleep situation and melatonin secretion patterns of schoolchildren may depend on whether the classroom seat where they spend a relatively long time during a school day is on the window side of the classroom. This study examined the relationship between classroom seat location and children's sleep situation and melatonin secretion patterns. Our subjects were 88 elementary school children (47 boys and 41 girls) from the 5th to 6th grades enrolled in public elementary schools in Tokyo; we analyzed the data of 73 (37 boys and 36 girls) with whom there was no data loss. The study was carried out on weekdays from September to October 2018. From the analysis, a 1.7-times difference in the average illuminance median was observed between seats that were on the window side and those on the corridor side (window side group: 362.2 lx, control group: 207.7 lx) In addition, the odds ratio of children with high melatonin (night to morning) was 10-times higher in the window side group than in the control group (OR＝10.179, 95％ CI＝1.492-69.455).
Based on our findings, we conclude that the sleep situation of children should be an important determinant in classroom seating.
Circadian rhythms play an important role in a wide range of human physiology and pathology. Individuals increasingly experience situations such as night-shift work schedules, likely leading to circadian disruption. Recent studies have also demonstrated that patients with other diseases often show symptoms of circadian disruption as manifested by the sleep–wake cycle and other biological rhythms. Circadian disruption often results in changes to the phase, period, and amplitude of the sleep–wake cycle, melatonin rhythm, and core body temperature. Several cardiometabolic, psychiatric, and neurodegenerative diseases are closely related to circadian disruption. Several interventions are also available, including phototherapy, exogenous melatonin, and exercise. The cumulative findings suggest that circadian disruption can increase risk for some cardiometabolic diseases. Circadian disruption also acts as a concomitant symptom of several psychiatric and neurodegenerative diseases. More attention should be paid to evaluating the impact of circadian disruption on these related diseases, as well as the benefits of the mitigation interventions for both circadian disruption and related diseases.
Jet lag is a circadian disruption that affects millions of people, resulting, among other things, in extreme sleepiness and memory loss. The hazardous implications of such effects are evident in situations in which focus and attention are required. Remarkably, there is a limited understanding of how jet lag recovery and associated memory loss vary year round under different photoperiods. Here we show, using different cycles representing winter, summer, and equinox in male mice, that jet lag recovery and memory vary significantly with photoperiod changes. We uncover a positive correlation of acute light effects on circadian-driven locomotion (known as negative masking) with photoentrainment speed and memory enhancement during jet lag. Specifically, we show that enhancing or reducing negative masking is correlated with better or worse memory performance, respectively. This study indicates that in addition to timed-light exposure for phase shifting, the negative masking response could also be biologically relevant when designing effective treatments of jet lag.
Our modern society and global economy require individuals to work under non-standard schedules to provide twenty-four-hour coverage for a large number of essential services. Despite the importance of these non-standard work schedules for production and logistical demands, they have a significant negative impact on the health of workers. Shift work and night work are recognized as risk factors for the development of a myriad of health-related problems due to the misalignment of circadian rhythms, chronic sleep deprivation, and exposure to light at night. The aim of this review is to provide an overview of the factors contributing to the detrimental effects of shift work on health and to highlight targeted interventions aimed at re-synchronizing the circadian system of those who work under shift schedules.
Mobility restrictions imposed to suppress coronavirus transmission can alter physical activity (PA) and sleep patterns. Characterization of response heterogeneity and their underlying reasons may assist in tailoring customized interventions. We obtained wearable data covering baseline, incremental movement restriction and lockdown periods from 1824 city-dwelling, working adults aged 21 to 40 years, incorporating 206,381 nights of sleep and 334,038 days of PA. Four distinct rest activity rhythms (RARs) were identified using k-means clustering of participants' temporally distributed step counts. Hierarchical clustering of the proportion of time spent in each of these RAR revealed 4 groups who expressed different mixtures of RAR profiles before and during the lockdown. Substantial but asymmetric delays in bedtime and waketime resulted in a 24 min increase in weekday sleep duration with no loss in sleep efficiency. Resting heart rate declined 2 bpm. PA dropped an average of 38%. 4 groups with different compositions of RAR profiles were found. Three were better able to maintain PA and weekday/weekend differentiation during lockdown. The least active group comprising 51 percent of the sample, were younger and predominantly singles. Habitually less active already, this group showed the greatest reduction in PA during lockdown with little weekday/weekend differences. Among different mobility restrictions, removal of habitual social cues by lockdown had the largest effect on PA and sleep. Sleep and resting heart rate unexpectedly improved. RAR evaluation uncovered heterogeneity of responses to lockdown and can identify characteristics of persons at risk of decline in health and wellbeing.
Biological rhythms evolved to provide temporal coordination across all tissues and organs and allow synchronization of physiology with predictable environmental cycles. Most important of these are circadian and circannual rhythms, primarily regulated via photoperiod signals from the retina. Understanding the nature of physiological rhythms in horses is crucially important for equine management. Predominantly, they have been removed from exposure to their natural environmental stimuli; the seasonally changing photoperiod, continuous foraging and feeding activity, social herd interactions, and the continuous low-intensity exercise of a grassland dweller. These have been replaced in many cases with confined indoor housing, regimental feeding and exercise times, social isolation, and exposure to lighting that is often erratic and does not come close to mimicking the spectral composition of sunlight. Man has further altered seasonal timing cues through the use of artificial lighting programs that impact reproductive behavior, breeding efficiency, and the development of youngstock. Understanding how these new environmental cues (some stronger and some weaker) impact the internal physiology of the horse in the context of the natural endogenous rhythms that evolved over millennia is key to helping to improve equine health, welfare, and performance, now and into the future. This review provides an overview of the field, highlights the recent discoveries related to biological timing in horses, and discusses the implications that these findings may have for the production and management of the elite equine athlete.
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.
Abstract: Natural daylight exposures in arctic regions vary substantially across seasons. Negative consequences have been observed in self-reports of sleep and daytime functions during the winter but have rarely been studied in detail. The focus of the present study set out to investigate sleep seasonality among indoor workers using objective and subjective measures. Sleep seasonality among daytime office workers (n = 32) in Kiruna (Sweden, 67.86° N, 20.23° E) was studied by comparing the same group of workers in a winter and summer week, including work and days off at the weekend, using actigraphs (motion loggers) and subjective ratings of alertness and mood. Actigraph analyses showed delayed sleep onset of 39 min in winter compared to the corresponding summer week (p < 0.0001) and shorter weekly sleep duration by 12 min (p = 0.0154). A delay of mid-sleep was present in winter at workdays (25 min, p < 0.0001) and more strongly delayed during days off (46 min, p < 0.0001). Sleepiness levels were higher in winter compared to summer (p < 0.05). Increased morning light exposure was associated with earlier mid-sleep (p < 0.001), while increased evening light exposure was associated with delay (p < 0.01). This study confirms earlier work that suggests that lack of natural daylight delays the sleep/wake cycle in a group of indoor workers, despite having access to electric lighting. Photic stimuli resulted in a general advanced sleep/wake rhythm during summer and increased alertness levels.
Many human action sequences, such as speaking and performing music, are inherently rhythmic: Sequence events are produced at quasi-regular temporal intervals. A wide range of interindividual variation has been noted in spontaneous production rates of these rhythmic action sequences. Dynamical theories of motor coordination suggest that individuals spontaneously produce rhythmic sequences at a natural frequency characterized by minimal energy expenditure and maximal temporal stability, relative to other frequencies. We tested this hypothesis by comparing the temporal variability with which musicians performed rhythmic melodies at their natural spontaneous rate with variability in their performances at faster and slower rates. Musicians’ temporal variability was lowest during performances at their spontaneous rate; in addition, performers’ tempo drift during trials at other rates showed bias toward their spontaneous rate. This study provides the first direct evidence that spontaneous rates of motor coordination represent optimally stable natural frequencies of endogenous rhythms.
Objective: This the first of two articles reviewing the scientific literature on the evaluation and treatment of circadian rhythm sleep disorders (CRSDs), employing the methodology of evidence-based medicine. In this first part of this paper, the general principles of circadian biology that underlie clinical evaluation and treatment are reviewed. We then report on the accumulated evidence regarding the evaluation and treatment of shift work disorder (SWD) and jet lag disorder (JLD). Methods: A set of specific questions relevant to clinical practice were formulated, a systematic literature search was performed, and relevant articles were abstracted and graded. Results: A substantial body of literature has accumulated that provides a rational basis the evaluation and treatment of SWD and JLD. Physiological assessment has involved determination of circadian phase using core body temperature and the timing of melatonin secretion. Behavioral assessment has involved sleep logs, actigraphy and the Morningness-Eveningness Questionnaire (MEQ). Treatment interventions fall into three broad categories: 1) prescribed sleep scheduling, 2) circadian phase shifting ("resetting the clock"), and 3) symptomatic treatment using hypnotic and stimulant medications. Conclusion: Circadian rhythm science has also pointed the way to rational interventions for the SWD and JLD, and these treatments have been introduced into the practice of sleep medicine with varying degrees of success. More translational research is needed, using subjects who meet current diagnostic criteria.
The human circadian timing system is most sensitive to the phase-shifting effects of light during the biological nighttime, a time at which humans are most typically asleep. The overlap of sleep with peak sensitivity to the phase-shifting effects of light minimizes the effectiveness of using light as a countermeasure to circadian misalignment in humans. Most current light exposure treatments for such misalignment are mostly ineffective due to poor compliance and secondary changes that cause sleep deprivation. Using a 16-day, parallel group design, we examined whether a novel sequence of light flashes delivered during sleep could evoke phase changes in the circadian system without disrupting sleep. Healthy volunteers participated in a 2-week circadian stabilization protocol followed by a 2-night laboratory stay. During the laboratory session, they were exposed during sleep to either darkness (n = 7) or a sequence of 2-msec light flashes given every 30 sec (n = 6) from hours 2 to 3 after habitual bedtime. Changes in circadian timing (phase) and micro- and macroarchitecture of sleep were assessed. Subjects exposed to the flash sequence during sleep exhibited a delay in the timing of their circadian salivary melatonin rhythm compared with the control dark condition (p < 0.05). Confirmation that the flashes penetrated the eyelids is presented by the occurrence of an evoked response in the EEG. Despite the robust effect on circadian timing, there were no large changes in either the amount or spectral content of sleep (p values > 0.30) during the flash stimulus. Exposing sleeping individuals to 0.24 sec of light spread over an hour shifted the timing of the circadian clock and did so without major alterations to sleep itself. While a greater number of matched subjects and more research will be necessary to ascertain whether these light flashes affect sleep, our data suggest that this type of passive phototherapy might be developed as a useful treatment for circadian misalignment in humans.
Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure.
Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m(2))-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m(2))-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time.
Sleep and chronobiology laboratory environment free of time cues.
Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD).
Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances.
Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders.
Burke TM; Markwald RR; Chinoy ED; Snider JA; Bessman SC; Jung CM; Wright Jr KP. Combination of light and melatonin time cues for phase advancing the human circadian clock. SLEEP 2013;36(11):1617-1624.
Rationale
We test methods to advance (shift earlier) circadian rhythms without producing misalignment between rhythms and sleep. We previously tested (1) a gradually advancing sleep/dark schedule plus morning bright light and afternoon/evening melatonin and (2) the same sleep schedule with only morning bright light. Now we report on the same sleep schedule with only afternoon/evening melatonin.
Objectives
This study aims to examine phase advances, sleepiness, and performance in response to melatonin compared to placebo.
Methods
Twelve adults (five female individuals) aged 20–45 years (mean ± SD = 28.3 ± 7.3 years) completed this within-subjects placebo-controlled counterbalanced study. The participants slept on fixed 8-h sleep schedules for nine days. Then, sleep/dark was advanced by 1 h/day for three consecutive days of treatment. The participants took 3 mg of melatonin or placebo 11 h before baseline sleep midpoint (the optimal time to produce phase advances) on the first treatment day and 1 h earlier on each subsequent day. We measured the dim light melatonin onset before and after treatment. The participants rated subjective symptoms throughout the study. They completed the Psychomotor Vigilance Task and rated sleepiness from 1 h before pill ingestion until bedtime on each treatment day.
Results
Melatonin produced significantly larger advances (1.3 ± 0.7 h) compared to placebo (0.7 ± 0.7 h); however, in the hours between melatonin ingestion and bed, melatonin caused sleepiness and performance decrements.
Conclusions
Adding afternoon/evening melatonin to the gradually advancing sleep schedule increased the phase advance, but given the side effects, like sleepiness, it is better to use morning bright light and perhaps a lower dose of melatonin.
There are three mechanisms that may contribute to the health, performance, and safety problems associated with night-shift work: (1) circadian misalignment between the internal circadian clock and activities such as work, sleep, and eating, (2) chronic, partial sleep deprivation, and (3) melatonin suppression by light at night. The typical countermeasures, such as caffeine, naps, and melatonin (for its sleep-promoting effect), along with education about sleep and circadian rhythms, are the components of most fatigue risk-management plans. We contend that these, while better than nothing, are not enough because they do not address the underlying cause of the problems, which is circadian misalignment. We explain how to reset (phase-shift) the circadian clock to partially align with the night-work, day-sleep schedule, and thus reduce circadian misalignment while preserving sleep and functioning on days off. This involves controlling light and dark using outdoor light exposure, sunglasses, sleep in the dark, and a little bright light during night work. We present a diagram of a sleep-and-light schedule to reduce circadian misalignment in permanent night work, or a rotation between evenings and nights, and give practical advice on how to implement this type of plan.
Regulation of circadian period in humans was thought to differ from that of other species, with the period of the activity
rhythm reported to range from 13 to 65 hours (median 25.2 hours) and the period of the body temperature rhythm reported to
average 25 hours in adulthood, and to shorten with age. However, those observations were based on studies of humans exposed
to light levels sufficient to confound circadian period estimation. Precise estimation of the periods of the endogenous circadian
rhythms of melatonin, core body temperature, and cortisol in healthy young and older individuals living in carefully controlled
lighting conditions has now revealed that the intrinsic period of the human circadian pacemaker averages 24.18 hours in both
age groups, with a tight distribution consistent with other species. These findings have important implications for understanding
the pathophysiology of disrupted sleep in older people.
The length of the free-running period (τ) affects how an animal re-entrains after phase shifts of the light-dark (LD) cycle. Those with shorter periods adapt faster to phase advances than those with longer periods, whereas those with longer periods adapt faster to phase delays than those with shorter periods. The free-running period of humans, measured in temporal isolation units and in forced desychrony protocols in which the day length is set beyond the range of entrainment, varies from about 23.5 to 26 h, depending on the individual and the experimental conditions (e.g., temporal isolation vs. forced desychrony). We studied 94 subjects free-running through an ultradian LD cycle, which was a forced desychrony with a day length of 4 h (2.5 h awake in dim light, ∼35 lux, alternating with 1.5 h for sleep in darkness). Circadian phase assessments were conducted before (baseline) and after (final) three 24-h days of the ultradian LD cycle. During these assessments, saliva samples were collected every 30 min and subsequently analyzed for melatonin. The phase shift of the dim light melatonin onset (DLMO) from baseline to final phase assessment gave the free-running period. The mean ± SD period was 24.31 ± .23 h and ranged from 23.7 to 24.9 h. Black subjects had a significantly shorter free-running period than Whites (24.18 ± .23 h, N =20 vs. 24.37 ± .22 h, N = 55). We had a greater proportion of women than men in our Black sample, so to check the τ difference we compared the Black women to White women. Again, Black subjects had a significantly shorter free-running period (24.18 ± .23, N = 17 vs. 24.41 ± .23, N = 23). We did not find any sex differences in the free-running period. These findings give rise to several testable predictions: on average, Blacks should adapt quicker to eastward flights across time zones than Whites, whereas Whites should adjust quicker to westward flights than Blacks. Also, Blacks should have more difficulty adjusting to night-shift work and day sleep, which requires a phase delay. On the other hand, Whites should be more likely to have trouble adapting to the early work and school schedules imposed by society. More research is needed to confirm these results and predictions. (Author correspondence: ceastman@rush.edu ).
Epidemiological studies link short sleep duration and circadian disruption with higher risk of metabolic syndrome and diabetes. We tested the hypotheses that prolonged sleep restriction with concurrent circadian disruption, as can occur in people performing shift work, impairs glucose regulation and metabolism. Healthy adults spent >5 weeks under controlled laboratory conditions in which they experienced an initial baseline segment of optimal sleep, 3 weeks of sleep restriction (5.6 hours of sleep per 24 hours) combined with circadian disruption (recurring 28-hour "days"), followed by 9 days of recovery sleep with circadian re-entrainment. Exposure to prolonged sleep restriction with concurrent circadian disruption, with measurements taken at the same circadian phase, decreased the participants' resting metabolic rate and increased plasma glucose concentrations after a meal, an effect resulting from inadequate pancreatic insulin secretion. These parameters normalized during the 9 days of recovery sleep and stable circadian re-entrainment. Thus, in humans, prolonged sleep restriction with concurrent circadian disruption alters metabolism and could increase the risk of obesity and diabetes.
Ocular light sensitivity is the primary mechanism by which the central circadian clock, located in the suprachiasmatic nucleus (SCN), remains synchronized with the external geophysical day. This process is dependent on both the intensity and timing of the light exposure. Little is known about the impact of the duration of light exposure on the synchronization process in humans. In vitro and behavioral data, however, indicate the circadian clock in rodents can respond to sequences of millisecond light flashes. In a cross-over design, we tested the capacity of humans (n = 7) to respond to a sequence of 60 2-msec pulses of moderately bright light (473 lux) given over an hour during the night. Compared to a control dark exposure, after which there was a 3.5±7.3 min circadian phase delay, the millisecond light flashes delayed the circadian clock by 45±13 min (p<0.01). These light flashes also concomitantly increased subjective and objective alertness while suppressing delta and sigma activity (p<0.05) in the electroencephalogram (EEG). Our data indicate that phase shifting of the human circadian clock and immediate alerting effects can be observed in response to brief flashes of light. These data are consistent with the hypothesis that the circadian system can temporally integrate extraordinarily brief light exposures.
To assess the effect of nocturnal light intensity on circadian adaptation to simulated night work.
Normal young men and women, simulated night work, home sleep.
We compared temperature rhythm phase shifts following timed exposure to high (approximately 5700 lux 3 hours/day), medium (approximately 1230 lux 3 hours/day) or constant low-intensity (< 250 lux) light during consecutive night shifts. Subjects (n = 35) followed a schedule of 7 days baseline, 6 days of 8-hour night shifts (with day sleep delayed 10 hours from baseline sleep), and 4 days of recovery. Subjects wore dark sunglasses while outdoors during daylight. Sleep logs were completed after each 8-hour sleep/dark period. Night work fatigue was rated by questionnaire.
During the 3rd through 5th days of night work, most subjects in the high and medium groups (100% and 85%) exhibited phase delays large enough that their body temperature minima occurred within the daytime sleep/dark period. Only 42% of subjects in the low group exhibited phase delays large enough to meet this criterion of circadian adaptation. The phase shifts of the high and medium groups were not significantly different, and were significantly different from the low group. Larger phase shifts were correlated with more sleep and less fatigue.
Extremely "bright" light may not be necessary for circadian adaptation in shift work situations similar to our study protocol (e.g., regular daytime sleep/dark periods, sunglasses).
To evaluate the effect of increasing the intensity and/or duration of exposure on light-induced changes in the timing of the circadian clock of humans.
Multifactorial randomized controlled trial, between and within subject design
General Clinical Research Center (GCRC) of an academic medical center
56 healthy young subjects (20-40 years of age)
Research subjects were admitted for 2 independent stays of 4 nights/3 days for treatment with bright or dim-light (randomized order) at a time known to induce phase delays in circadian timing. The intensity and duration of the bright light were determined by random assignment to one of 9 treatment conditions (duration of 1, 2, or 3 hours at 2000, 4000, or 8000 lux).
Treatment-induced changes in the dim light melatonin onset (DLMO) and dim light melatonin offset (DLMOff) were measured from blood samples collected every 20-30 min throughout baseline and post-treatment nights. Comparison by multi-factor analysis of variance (ANOVA) of light-induced changes in the time of the circadian melatonin rhythm for the 9 conditions revealed that changing the duration of the light exposure from 1 to 3 h increased the magnitude of light-induced delays. In contrast, increasing from moderate (2,000 lux) to high (8,000 lux) intensity light did not alter the magnitude of phase delays of the circadian melatonin rhythm.
Results from the present study suggest that for phototherapy of circadian rhythm sleep disorders in humans, a longer period of moderate intensity light may be more effective than a shorter exposure period of high intensity light.
Melatonin and light treatment are recommended for hastening adaptation to time zone change. We evaluated an afternoon regimen of 3 mg sustained release (SR) melatonin with and without next morning green light treatment for circadian phase advance. Effects of melatonin and light were tested separately and then combined to determine if the total phase change is additive or synergistic.
For each condition (melatonin, placebo, light, melatonin plus light), 11 subjects spent from Tuesday evening until Friday afternoon in the laboratory. For all four conditions, the following sleep schedule was maintained: night 1, 2345 to 0630 hours, night 2, 1600 to 0530 hours, and night 3, 2345 to 0700 hours. For the light-only condition, light treatment was administered between 0700 and 0800 hours on Thursday. For melatonin-only or placebo conditions, capsules were administered at 1600 hours on Wednesday. For the combined condition, melatonin was administered at 1600 hours on Wednesday with light treatment between 0600 and 0700 hours on Thursday. Circadian phase was assessed by calculating dim light melatonin onset (DLMO) from salivary melatonin, using a mean baseline +2 standard deviations (BL+2 SD) threshold. For all four conditions, pre-treatment and post-treatment DLMO assessments were on Tuesday and Thursday evenings, respectively.
Phase advances were: melatonin at 1600 hours, 0.72 h p<0.005, light treatment from 0700 to 0800 hours, 0.31 h, non-significant, and the combined treatment, 1.04 h p<0.0002.
The phase advance from the combination of afternoon melatonin with next morning light is additive.
In 2007, the International Agency for Research on Cancer (IARC) classified shift work with circadian disruption or chronodisruption as a probable human carcinogen. Short-term disturbances of biological 24-hour-rhythms following exposures to light and darkness at unusual times are well-known as "jet-lag" and "shift-lag" symptoms. However, that chronic disturbances or disruptions of timely sequenced circadian rhythms (chronodisruption) should contribute to long-term developments of cancer is a relatively new concept. This review provides background and practical information with regard to the open question "does shift-work cause cancer?"
Overview on the basis of a selective literature search via Medline and ISI Web of Knowledge until 2009 from the viewpoints of occupational medicine, epidemiology, chronobiology, and occupational science.
The postulated causal links between shift-work and cancer in humans are biologically plausible in the light of experimental findings, but to date we lack epidemiological studies which could describe or exonerate risks in humans. Monetary compensation has already been paid for such cases in at least one country (Denmark). In Germany, however, according to the applicable law, a new occupational disease can only be recognized when certain conditions for the recognition of "general scientific merit" have been met. We present the current state of knowledge regarding prevention.
While causal links between shift-work and cancer developments are not established, future shift-work planning should pay more attention to insights from occupational medicine, chronobiology, and occupational science.
Phase response curves (PRCs) to melatonin exist, but none compare different doses of melatonin using the same protocol.
The aim was to generate a PRC to 0.5 mg of oral melatonin and compare it to our previously published 3.0 mg PRC generated using the same protocol.
The study included two 5-d sessions in the laboratory, each preceded by 7-9 d of fixed sleep times. Each session started and ended with a phase assessment to measure the dim light melatonin onset (DLMO). In between were 3 d in an ultradian dim light (<150 lux)/dark cycle (light:dark, 2.5:1.5).
Healthy adults (16 men, 18 women) between the ages of 18 and 42 yr participated in the study.
During the ultradian days of the laboratory sessions, each participant took one pill per day at the same clock time (0.5 mg melatonin or placebo, double blind, counterbalanced).
Phase shifts to melatonin were derived by subtracting the phase shift to placebo. A PRC with time of pill administration relative to baseline DLMO and a PRC relative to midpoint of home sleep were generated.
Maximum advances occurred when 0.5 mg melatonin was taken in the afternoon, 2-4 h before the DLMO, or 9-11 h before sleep midpoint. The time for maximum phase delays was not as distinct, but a fitted curve peaked soon after wake time.
The optimal administration time for advances and delays is later for the lower dose of melatonin. When each dose of melatonin is given at its optimal time, both yield similarly sized advances and delays.
This article describes in detail how melatonin, bright light, and sleep schedules can be used in conjunction with currently available flight times to reduce or eliminate jet lag. The goal is to educate circadian rhythm researchers and sleep clinicians about the principles involved so that they can make similar jet travel schedules customized for individuals traveling in any direction across multiple time zones.
To assess night shift improvements in mood, fatigue, and performance when the misalignment between circadian rhythms and a night shift, day sleep schedule is reduced.
Blocks of simulated night shifts alternated with days off. Experimental subjects had interventions to delay their circadian clocks to partially align with a night shift schedule. Control subjects had no interventions. Subjects were categorized according to the degree of circadian realignment independent of whether they were in the experimental or control groups. Twelve subjects were categorized as not re-entrained, 21 as partially re-entrained, and 6 as completely re-entrained.
Home sleep and laboratory night shifts.
Young healthy adults.
Experimental subjects had intermittent bright light pulses during night shifts, wore dark sunglasses outside, and had scheduled sleep episodes in darkness.
A computerized test battery was administered every 2 hours during day and night shifts. After about one week on the night shift schedule, which included a weekend off, the partially and completely re-entrained groups had markedly improved mood, fatigue, and performance compared to the group that was not re-entrained. The completely and partially re-entrained groups were similar to each other and had levels of mood, fatigue, and performance that were close to daytime levels.
Partial re-entrainment to a permanent night shift schedule, which can be produced by feasible, inexpensive interventions, is associated with greatly reduced impairments during night shifts.
The length of the endogenous period of the human circadian clock (tau) is slightly greater than 24 hours. There are individual differences in tau, which influence the phase angle of entrainment to the light/dark (LD) cycle, and in doing so contribute to morningness-eveningness. We have recently reported that tau measured in subjects living on an ultradian LD cycle averaged 24.2 hours, and is similar to tau measured using different experimental methods. Here we report racial differences in tau. Subjects lived on an ultradian LD cycle (1.5 hours sleep, 2.5 hours wake) for 3 days. Circadian phase assessments were conducted before and after the ultradian days to determine the change in circadian phase, which was attributed to tau. African American subjects had a significantly shorter tau than subjects of other races. We also tested for racial differences in our previous circadian phase advancing and phase delaying studies. In the phase advancing study, subjects underwent 4 days of a gradually advancing sleep schedule combined with a bright light pulse upon awakening each morning. In the phase delaying study, subjects underwent 4 days of a gradually delaying sleep schedule combined with evening light pulses before bedtime. African American subjects had larger phase advances and smaller phase delays, relative to Caucasian subjects. The racial differences in tau and circadian phase shifting have important implications for understanding normal phase differences between individuals, for developing solutions to the problems of jet lag and shift work, and for the diagnosis and treatment of circadian rhythm based sleep disorders such as advanced and delayed sleep phase disorder.
The human circadian system is maximally sensitive to short-wavelength (blue) light. In a previous study we found no difference between the magnitude of phase advances produced by bright white versus bright blue-enriched light using light boxes in a practical protocol that could be used in the real world. Since the spectral sensitivity of the circadian system may vary with a circadian rhythm, we tested whether the results of our recent phase-advancing study hold true for phase delays. In a within-subjects counterbalanced design, this study tested whether bright blue-enriched polychromatic light (17000 K, 4000 lux) could produce larger phase delays than bright white light (4100 K, 5000 lux) of equal photon density (4.2x10(15) photons/cm(2)/sec). Healthy young subjects (n = 13) received a 2 h phase delaying light pulse before bedtime combined with a gradually delaying sleep/dark schedule on each of 4 consecutive treatment days. On the first treatment day the light pulse began 3 h after the dim light melatonin onset (DLMO). An 8 h sleep episode began at the end of the light pulse. Light treatment and the sleep schedule were delayed 2 h on each subsequent treatment day. A circadian phase assessment was conducted before and after the series of light treatment days to determine the time of the DLMO and DLMOff. Phase delays in the blue-enriched and white conditions were not significantly different (DLMO: -4.45+/-2.02 versus -4.48+/-1.97 h; DLMOff: -3.90+/-1.97 versus -4.35+/-2.39 h, respectively). These results indicate that at light levels commonly used for circadian phase shifting, blue-enriched polychromatic light is no more effective than the white polychromatic lamps of a lower correlated color temperature (CCT) for phase delaying the circadian clock.
Scheduled bright light and darkness can phase shift the circadian clocks of night workers for complete adaptation to a night work, day sleep schedule, but few night workers would want this because it would leave them out of phase with the diurnal world on days off. This is the final study in a series designed to produce a compromise circadian phase position for permanent night shift work in which the sleepiest circadian time is delayed out of the night work period and into the first half of the day sleep episode. The target compromise phase position was a dim light melatonin onset (DLMO) of 3:00, which puts the sleepiest circadian time at approximately 10:00. This was predicted to improve night shift alertness and performance while permitting sufficient daytime sleep after work as well as late-night sleep on days off. In a between-subjects design, 19 healthy subjects underwent 3 simulated night shifts (23:00-7:00), 2 days off, 4 more night shifts, and 2 more days off. Subjects "worked" in the lab and slept at home. Experimental subjects received four 15-min bright light pulses during each night shift, wore dark sunglasses when outside, slept in dark bedrooms at scheduled times, and received outdoor afternoon light exposure ("light brake") to keep their rhythms from delaying too far. Control subjects remained in normal room light during night shifts, wore lighter sunglasses, and had unrestricted sleep and outdoor light exposure. The final DLMO of the experimental group was 3:22 +/- 2.0 h, close to the target of 3:00, and later than the control group at 23:24 +/- 3.8 h. Experimental subjects slept for nearly all the permitted time in bed. Some control subjects who slept late on weekends also reached the compromise phase position and obtained more daytime sleep. Subjects who phase delayed (whether in the experimental or control group) close to the target phase performed better during night shifts. A compromise circadian phase position improved performance during night shifts, allowed sufficient sleep during the daytime after night shifts and during the late nighttime on days off, and can be produced by inexpensive and feasible interventions.
Studies in humans and mice revealed that circadian phase shifting effects of light are larger at the beginning of a light exposure interval than during subsequent exposure. Little is known about the dynamics of this response reduction phenomenon. Here the authors propose a method to obtain information on the progression of phase during light exposure. Phase response curves to intervals of light exposure over a wide range in duration are available for flesh flies, mice, and humans. By comparing the phase shifts induced by pulses of various durations but starting at the same circadian phase, the progression of phase during a long interval (hours) of light exposure is reconstructed for each of these 3 species. For flies, the phase progression curves show that light pulses-if long enough- eventually make the pacemaker stabilize around InT18 (near subjective dusk), as is typical for strong resetting. The progression of phase toward the final value never shows advances larger than 7 h, while delays can be as large as 18 h. By applying the phase progression curve method presented in this study, differences between advances and delays in type-0 phase response curves can be distinguished clearly. In flesh flies (Sarcophaga) this bifurcation between delays and advance occurs when light exposure starts at InT0 (subjective midnight). The present study confirms earlier findings in mice showing that the beginning of the light pulse generates stronger phase shifts than subsequent hours of light. Response reduction is complete within 1 h of exposure. It is argued that the variation is not so much due to light adaptation processes, but rather to response saturation. In contrast to light adaptation, response saturation is fundamental to proper functioning of the circadian pacemaker during natural entrainment. For understanding entrainment of the pacemaker to natural light, phase progression curves in which naturalistic light profiles are applied could be an important tool.
There is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes, and cardiovascular disease, perhaps the result of physiologic maladaptation to chronically sleeping and eating at abnormal circadian times. To begin to understand underlying mechanisms, we determined the effects of such misalignment between behavioral cycles (fasting/feeding and sleep/wake cycles) and endogenous circadian cycles on metabolic, autonomic, and endocrine predictors of obesity, diabetes, and cardiovascular risk. Ten adults (5 female) underwent a 10-day laboratory protocol, wherein subjects ate and slept at all phases of the circadian cycle-achieved by scheduling a recurring 28-h "day." Subjects ate 4 isocaloric meals each 28-h "day." For 8 days, plasma leptin, insulin, glucose, and cortisol were measured hourly, urinary catecholamines 2 hourly (totaling approximately 1,000 assays/subject), and blood pressure, heart rate, cardiac vagal modulation, oxygen consumption, respiratory exchange ratio, and polysomnographic sleep daily. Core body temperature was recorded continuously for 10 days to assess circadian phase. Circadian misalignment, when subjects ate and slept approximately 12 h out of phase from their habitual times, systematically decreased leptin (-17%, P < 0.001), increased glucose (+6%, P < 0.001) despite increased insulin (+22%, P = 0.006), completely reversed the daily cortisol rhythm (P < 0.001), increased mean arterial pressure (+3%, P = 0.001), and reduced sleep efficiency (-20%, P < 0.002). Notably, circadian misalignment caused 3 of 8 subjects (with sufficient available data) to exhibit postprandial glucose responses in the range typical of a prediabetic state. These findings demonstrate the adverse cardiometabolic implications of circadian misalignment, as occurs acutely with jet lag and chronically with shift work.
To produce a compromise circadian phase position for permanent night shift work in which the sleepiest circadian time is delayed out of the night work period and into the first half of the day sleep period. This is predicted to improve night shift alertness and performance while permitting adequate late night sleep on days off.
Between-subjects.
Home and laboratory.
24 healthy subjects.
Subjects underwent 3 simulated night shifts, 2 days off, and 4 more night shifts. Experimental subjects received five, 15 minute bright light pulses from light boxes during night shifts, wore dark sunglasses when outside, slept in dark bedrooms at scheduled times after night shifts and on days off, and received outdoor afternoon light exposure (the "light brake"). Control subjects remained in normal room light during night shifts, wore lighter sunglasses, and had unrestricted sleep and outdoor light exposure.
The final dim light melatonin onset (DLMO) of the experimental group was approximately approximately 04:30, close to our target compromise phase position, and significantly later than the control group at approximately 00:30. Experimental subjects performed better than controls, and slept for nearly all of the allotted time in bed. By the last night shift, they performed almost as well during the night as during daytime baseline. Controls demonstrated pronounced performance impairments late in the night shifts, and exhibited large individual differences in sleep duration.
Relatively inexpensive and feasible interventions can produce adaptation to night shift work while still allowing adequate nighttime sleep on days off.
Previous studies have shown that the human circadian system is maximally sensitive to short-wavelength (blue) light. Whether this sensitivity can be utilized to increase the size of phase shifts using light boxes and protocols designed for practical settings is not known. We assessed whether bright polychromatic lamps enriched in the short-wavelength portion of the visible light spectrum could produce larger phase advances than standard bright white lamps.
Twenty-two healthy young adults received either a bright white or bright blue-enriched 2-h phase advancing light pulse upon awakening on each of four treatment days. On the first treatment day the light pulse began 8h after the dim light melatonin onset (DLMO), on average about 2h before baseline wake time. On each subsequent day, light treatment began 1h earlier than the previous day, and the sleep schedule was also advanced.
Phase advances of the DLMO for the blue-enriched (92+/-78 min, n=12) and white groups (76+/-45 min, n=10) were not significantly different.
Bright blue-enriched polychromatic light is no more effective than standard bright light therapy for phase advancing circadian rhythms at commonly used therapeutic light levels.
Multiple experimental approaches have been used to assess the free-running period, or “tau,” of humans. One approach has been to study circadian rhythms in free-running blind humans. For example, Sack et al. (1992) measured the plasma melatonin rhythm in 11 free-running blind people and reported an average tau of 24.55 h.
The prevalence of hazardous incidents induced by attentional impairment during night work and ensuing commute times is attributable to circadian misalignment and increased sleep pressure. In a 10-day shift work simulation protocol (4 day shifts and 3 night shifts), the efficacies of 2 countermeasures against nighttime (2300 to 0700 h) attentional impairment were compared: (1) Morning Sleep (0800 to 1600 h; n = 18) in conjunction with a phase-delaying light exposure (2300 to 0300 h), and (2) Evening Sleep (1400 to 2200 h; n = 17) in conjunction with a phase-advancing light exposure (0300 to 0700 h). Analysis of the dim light salivary melatonin onset indicated a modest but significant circadian realignment in both sleep groups (evening sleep: 2.27 +/- 0.6 h phase advance, p < 0.01; morning sleep: 4.98 +/- 0.43 h phase delay, p < 0.01). Daytime sleep efficiency and total sleep time did not differ between them or from their respective baseline sleep (2200 to 0600 h; p > 0.05). However, on the final night shift, the evening sleep subjects had 37% fewer episodes of attentional impairment (long response times: 22 +/- 4 vs. 35 +/- 4; p = 0.02) and quicker responses (p < 0.01) on the Psychomotor Vigilance Task than their morning sleep counterparts. Their response speed recovered to near daytime levels (p = 0.47), whereas those of the morning sleep subjects continued to be slower than their daytime levels (p = 0.008). It is concluded that partial circadian realignment to night work in combination with reduced homeostatic pressure contributed to the greater efficacy of a schedule of Evening Sleep with a phase-advancing light exposure as a countermeasure against attentional impairment, over a schedule of Morning Sleep with a phase-delaying light exposure. These results have important implications for managing patients with shift work disorder.
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.
Male subjects had their sleep schedules shifted 12 h to accommodate eight or more consecutive simulated night shifts. They were exposed to artificial light (approximately 5,000 lux, 3- to 6-h durations) each night, slept at home in very dark bedrooms during the day, and wore dark welders goggles whenever they went outside during daylight. Body temperature was continuously measured, and daily questionnaires provided estimates of sleep time and mood. The circadian temperature rhythm phase shifted, usually approximately 2 h/day, in 21 of 24 subjects. The temperature rhythms of the other three subjects appeared to remain entrained to the 24-h zeitgebers. In the subjects whose temperature rhythms shifted, the direction of shift (advance or delay) depended on the timing of light exposure relative to the baseline temperature phase, consistent with a phase-response curve. Sleep was disturbed, and fatigue was increased during the first few days after the shift of the sleep-wake schedule.
Using 'classical' experimental protocols, a human phase-response curve (PRC) to a single 3-h bright light pulse has been established. When the light pulse was centred slightly before the time of body temperature minimum, the circadian system delayed, whilst a pulse slightly after the minimum advanced it. Maximum phase shifts were about 2 h. When light pulses over 3 successive cycles were used, larger shifts (4-7 h) were produced. It is concluded that the human PRC does not differ in principle from that found in other species, except with respect to the light intensity required.
The development and use of a new scale, the Epworth sleepiness scale (ESS), is described. This is a simple, self-administered questionnaire which is shown to provide a measurement of the subject's general level of daytime sleepiness. One hundred and eighty adults answered the ESS, including 30 normal men and women as controls and 150 patients with a range of sleep disorders. They rated the chances that they would doze off or fall asleep when in eight different situations commonly encountered in daily life. Total ESS scores significantly distinguished normal subjects from patients in various diagnostic groups including obstructive sleep apnea syndrome, narcolepsy and idiopathic hypersomnia. ESS scores were significantly correlated with sleep latency measured during the multiple sleep latency test and during overnight polysomnography. In patients with obstructive sleep apnea syndrome ESS scores were significantly correlated with the respiratory disturbance index and the minimum SaO2 recorded overnight. ESS scores of patients who simply snored did not differ from controls.
Laboratory studies suggest that evening light before bedtime can suppress melatonin. Here, we measured the range of evening light intensity people can generate with their household lights, and for the first time determined if varying home light before usual bedtime can shift circadian phase. This was a 3‐week study with two counterbalanced conditions separated by a 5‐day break. In a dim week, eight healthy subjects minimized their home light exposure from 4 h before habitual bedtime until a self‐selected bedtime. In a bright week, the subjects maximized their home lighting for the same time. The dim light melatonin onset (DLMO) was assessed after each week. On average subjects maximized their lights to approximately 65 lux and minimized their lights to approximately 3 lux. Wrist actigraphy indicated that subjects went to bed slightly later when lights were maximized (average 14 min later, P = 0.05), but wake time did not change. Every subject had a later DLMO after the week of maximum versus minimum light exposure (average 1:03 h later, P Document Type: Research Article DOI: http://dx.doi.org/10.1111/php.12241 Publication date: May 1, 2014 $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function() { $(".shortdescription").hide(); $(".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Optics & Light By this author: Burgess, Helen J. ; Molina, Thomas A. GA_googleFillSlot("Horizontal_banner_bottom");