Article

Resetting the late timing of ‘night owls’ has a positive impact on mental health and performance

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Abstract

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.

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... Furthermore, because the daily routine of religious communities is usually strongly oriented towards getting up early and going to bed early, without considering individual chronotype, we also suppose that persons with late circadian timing, so-called "night owls", are, to some extent, handicapped by this regime. As opposed to "larks" with an early circadian timing, "night owls" prefer to stay up and to work long in the evening and have problems waking up and being active early in the morning [27]. "Night owls" living in a religious community with a structured daily routine may suffer from lack of sleep, which may have a negative impact on their health [28]. ...
... A common daily routine in a religious community is strictly oriented to getting up early and going to bed early, which is favorable for "larks" and inconvenient for "owls", who have to adapt to this routine. To some extent, shifting sleep/wake timings in "night owls" to earlier hours may have a positive effect on their performance and mental health [27]. However, their biorhythm may still cause difficulties with falling asleep too early. ...
... Our sample is too small to discuss this topic; however, evening types were shown to have worse health characteristics. The connection between being a "night owl CP" and a higher risk of depression is consistent with general findings about this chronotype [27]. Furthermore, these CP may be stressed by the permanent lack of sleep, which can contribute to the development of depression. ...
Article
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This study examines the general health of consecrated persons (CP) in the Czech Republic (CZ) and in Slovakia (SK) compared to control samples of the Czech population. The sample of 293 CP participants (age: M = 47.52, SD = 9.57, females: 78.88%, 180 Czechs, 213 Slovaks) was compared with two control samples, one of which was nationally representative. Comparing CP with the general population, we measured the frequency of recent health complaints, the occurrence of chronic illnesses, general health and the individual chronotype. Compared to the representative sample, CP had a higher chance of suffering from pelvis minor pain and obesity but a lower chance of diabetes. Furthermore, CP had higher odds of having worse general health. Comparing “larks” with “night owls” among CP, the “night owls” had a significantly higher chance of suffering from worse general health. “Night owl” CP also seem to suffer more from backache and depression/anxiety and to have more problems with falling asleep. Compared to the overall society, CP in CZ and SK tend to have similar or worse general health. The results differ from the findings in the US, pointing to the positive health effects of the spiritual experience and structured daily routine of CP. Thus, this study shows the importance of more detailed research on the way of life of Czech and Slovak CP to determine the factors with the most negative health effects.
... Experimental work utilizing protocols to increase adolescent sleep duration and manipulate sleep timing have shown promise outside the school environment [84,85]. Although adolescents have a propensity for late sleep, the ability to extend sleep through the introduction of earlier bedtimes is an interesting possibility that should not be overlooked. ...
... Therefore, an intervention that successfully phase advances, in other words that shifts late timing to an earlier time, could be beneficial. Facer-Childs et al. [85] conducted a field study that aimed to phase advance the sleep/wake timings of an older adolescent sample (average age of 21.3 years) of late chronotypes, classified using the Munich Chronotype Questionnaire. The experimental group in this randomized controlled trial received an intervention schedule to follow for three weeks. ...
... This provided sleep hygiene instructions and targeted appropriately timed light exposure through earlier wake/sleep times, fixed meal times, caffeine intake and exercise. These participants demonstrated a phase advance of around two hours in sleep/wake timing post-intervention: a positive finding that suggests timing can be shifted in a real-world setting to align more closely to societal demands [85]. ...
Article
Sleep is vital for our physical, emotional and cognitive health. However, adolescents face many challenges where their sleep is concerned. This is reflected in their sleep patterns including the timing of their sleep and how much sleep they achieve on a regular basis: their sleep is characteristically delayed and short. Notably, insufficient sleep is associated with impairments in adolescent functioning. Endogenous and exogenous factors are known to affect sleep at this age. Alterations in the bioregulation of sleep, comprising the circadian timing system and the sleep/wake homeostatic system, represent the intrinsic mechanisms at work. Compounding this, environmental, psychosocial and lifestyle factors may contribute to shortened sleep. This review discusses the amount of sleep gained by adolescents and its implications, the challenges to adolescent sleep and the interventions introduced in an effort to prioritize sleep health in this important developmental period.
... 29,30 The experimental advance shift of evening-type late timing with light exposure, behavioral measures and exercise leads to significant improvement in selfreported depression. 31 Such modulation of brain physiology by circadian rhythms was recently shown to be underpinned by changes in cortical excitability, which is enhanced and associated with improved cognitive performance at the preferred time of the day. 32 Interestingly, impaired cortical excitability and brain plasticity have also been reported in depression. ...
... The population consisted of 77% women, of median (IQR) age 39 (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48) years. Two-thirds of participants were employees with daytime working hours before the confinement and worked from home during the lockdown. ...
Article
Full-text available
Purpose: The containment of the population during the COVID-19 pandemic led to the emergence or recurrence of psychiatric conditions and sleep disorders. The influence of sleep/wake rhythm on mental health is well known. The objective of our study was to evaluate the link between the shift in sleep/wake rhythm and the presence of depressive symptoms during the March to May 2020 lockdown in the French population. Participants and methods: Participants (n = 2513) were recruited via newspapers and social networks in March 2020. We evaluated i) the chronotype before and during the lockdown, assessed by the change in mid-sleep time on work-free days corrected for sleep debt on workdays (delta MSFsc); ii) morningness-eveningness circadian preference (Horne & Ostberg questionnaire); iii) depressive symptoms (Patient Health Questionnaire-9, PHQ-9). The delta MSFsc and the PHQ-9 score were compared between circadian preference types. A multivariate model adjusted for age, sex, circadian preference, housing type, and marital status was used to assess the influence of delta MSFsc on the PHQ-9 score in the whole population. Results: The population consisted of 77% women, of median (IQR) age 39 (30-48) years. Compared with the pre-lockdown period, the median (IQR) MSFsc was shifted by 30 (0-66) min during the lockdown, with a significant difference between evening [60 (15-120) min], morning [15 (0-46) min] and neutral [30 (0-70) min] circadian type individuals, p < 0.001. One-third of all participants had moderate to severe depressive symptoms (PHQ-9 ≥ 10). A 1-hour shift in MSFsc was associated with a 0.50-point increase [95% CI (0.28; 0.72), p < 0.001] in the PHQ-9. Conclusion: A phase delay in the chronotype was observed in the general population during lockdown. Such disruption was associated with depressive symptoms but the direction of the relationship remains hypothetical. The impact on mental health of preventive measures targeting the sleep/wake rhythm in this context needs further evaluation.
... 29,30 The experimental advance shift of evening-type late timing with light exposure, behavioral measures and exercise leads to significant improvement in selfreported depression. 31 Such modulation of brain physiology by circadian rhythms was recently shown to be underpinned by changes in cortical excitability, which is enhanced and associated with improved cognitive performance at the preferred time of the day. 32 Interestingly, impaired cortical excitability and brain plasticity have also been reported in depression. ...
... The population consisted of 77% women, of median (IQR) age 39 (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48) years. Two-thirds of participants were employees with daytime working hours before the confinement and worked from home during the lockdown. ...
Article
Juliette Felician,1– 3 Filipe Galvao,3 Mylène Lefebvre,3 Mikail Nourredine,2,4– 6,* Laure Peter-Derex1,2,7,* 1Centre for Sleep Medicine and Respiratory Diseases, Hôpital de la Croix-Rousse, Hospices Civils de Lyon, Lyon, France; 2Medicine faculty, Lyon 1 University, Lyon, France; 3Unité Michel Jouvet – Pôle Est – Z19, Centre Hospitalier Le Vinatier, Bron, France; 4Biostatistics Unit, University Hospital Service of Pharmacotoxicology and Public Health Department, Hospices Civils de Lyon, Lyon, France; 5Research Department, Centre Hospitalier Le Vinatier, Bron, France; 6Biometry and Evolutionary Biology Laboratory, UMR CNRS 5558, Lyon, France; 7Lyon Neuroscience Research Centre, CNRS UMR 5292/INSERM U1028, Lyon, France*These authors contributed equally to this workCorrespondence: Laure Peter-Derex, Centre for Sleep Medicine and Respiratory Diseases, Hôpital de la Croix-Rousse, Hospices Civils de Lyon, 103 Grande Rue de la Croix-Rousse, Lyon, 69004, France, Tel +33 4 72 07 17 69, Fax +33 4 72 07 28 08, Email laure.peter-derex@chu-lyon.frPurpose: The containment of the population during the COVID-19 pandemic led to the emergence or recurrence of psychiatric conditions and sleep disorders. The influence of sleep/wake rhythm on mental health is well known. The objective of our study was to evaluate the link between the shift in sleep/wake rhythm and the presence of depressive symptoms during the March to May 2020 lockdown in the French population.Participants and Methods: Participants (n = 2513) were recruited via newspapers and social networks in March 2020. We evaluated i) the chronotype before and during the lockdown, assessed by the change in mid-sleep time on work-free days corrected for sleep debt on workdays (delta MSFsc); ii) morningness-eveningness circadian preference (Horne & Ostberg questionnaire); iii) depressive symptoms (Patient Health Questionnaire-9, PHQ-9). The delta MSFsc and the PHQ-9 score were compared between circadian preference types. A multivariate model adjusted for age, sex, circadian preference, housing type, and marital status was used to assess the influence of delta MSFsc on the PHQ-9 score in the whole population.Results: The population consisted of 77% women, of median (IQR) age 39 (30– 48) years. Compared with the pre-lockdown period, the median (IQR) MSFsc was shifted by 30 (0– 66) min during the lockdown, with a significant difference between evening [60 (15– 120) min], morning [15 (0– 46) min] and neutral [30 (0– 70) min] circadian type individuals, p < 0.001. One-third of all participants had moderate to severe depressive symptoms (PHQ-9 ≥ 10). A 1-hour shift in MSFsc was associated with a 0.50-point increase [95% CI (0.28; 0.72), p < 0.001] in the PHQ-9.Conclusion: A phase delay in the chronotype was observed in the general population during lockdown. Such disruption was associated with depressive symptoms but the direction of the relationship remains hypothetical. The impact on mental health of preventive measures targeting the sleep/wake rhythm in this context needs further evaluation.Keywords: phase delay, pandemic, containment, mental health, chronotype, circadian preference
... This can be seen in the developmental shift toward eveningness during adolescence, which has been related to higher negative moods and lower well-being (Díaz-Morales, Escribano, & Jankowski, 2015). Moreover, in laboratory conditions, earlier shift in sleep-timing was found to lead to a decrease in depression and stress and improvement in the well-being of evening-types (Facer-Childs, Middleton, Skene, & Bagshaw, 2019). Similarly, an earlier shift in depressive patients has been reported to improve mood states (Zaki et al., 2017). ...
... The results showed that earlier shift in sleeptiming was related to better mood and well-being. This has been shown earlier in the general population (Facer-Childs et al., 2019;Hasler, Buysse, & Germain, 2015) and in depressive patients (Zaki et al., 2017). Contrastingly, a shift toward eveningness during adolescence has been related to higher negative moods and lower well-being (Díaz-Morales et al., 2015). ...
Article
It is suggested that social obligations, such as early work/school starts, have a disadvantageous impact on sleep behavior that can further transfer to mental health problems. Lockdown as a result of the COVID-19 pandemic created a unique opportunity to research human sleep-wake behavior in naturalistic conditions of decreased social obligations. This study aimed to test whether a change in habitual sleep-wake timing (shift in chronotype) during the COVID-19 lockdown impacted mood and well-being, and whether the impact differs according to morningness-eveningness preference. University students (N = 1011; Meanage = 21.95 ± 1.95 years) filled out self-report questionnaires containing measures of chronotype (midpoint of sleep) before and during the COVID-19 lockdown, morningness-eveningness preference, mood, and well-being. The impact of morningness-eveningness preference and shift in chronotype was tested via multiple regression analyses. Results showed that participants shifted their chronotype in line with their morningness-eveningness preference, and that shift toward earlier sleep-wake timing was related to better moods and well-being. Moreover, higher levels of positive mood (vigor) and well-being were found in individuals who shifted their sleep-wake timing earlier and were higher on morningness.
... It is typically conceptualized as a continuous unidimensional spectrum from morningness to eveningness with a broadly normal distribution (Gaspar-Barba et al. 2009;Roenneberg et al. 2004Roenneberg et al. , 2003. Chronotype is a product of both genetics and environment (Facer-Childs et al. 2019;Hu et al. 2016;Lane et al. 2016), and is expressed as diurnal variations in characteristics such as energy levels, affect, and both cognitive and physical performance (Facer-Childs et al. 2018;Goldstein et al. 2007;Merrow et al. 2005;Miller et al. 2015). ...
... However, research on insomnia's effect on subsequent mood and mental health outcomes (e.g. Bernert et al. 2017;Littlewood et al. 2019) combined with research on chronotype's causal association with poor sleep quality points toward a directional chronotype-insomnia-affect pathway (Bakotic et al. 2017;Facer-Childs et al. 2019;Konjarski et al. 2018). This putative causal relationship is supported by the results of the present study. ...
Article
Full-text available
Chronotype describes a person’s general preference for mornings, evenings, or neither. It is typically conceptualized as a continuous unidimensional spectrum from morningness to eveningness. Eveningness is associated with poorer outcomes across a myriad of physical and mental health outcomes. This preference for later sleep and wake times is associated with increased risk of depression, anxiety, and suicidal ideation in both clinical and community samples. However, the mechanisms underlying the negative consequences of this preference for evenings are not fully understood. Previous research has found that sleep disturbances may act as a mediator of this relationship. The present study aimed to explore the associations between chronotype and affective outcomes in a sample of students. Additionally, it aimed to investigate the potential role of insomnia as a mediator within these relationships. Participants (n = 190) completed an anonymous self-report survey of validated measures online which assessed chronotype, insomnia symptoms, and a range of affective outcomes (defeat, entrapment, suicide risk, stress, and depressive and anxious symptomology). Eveningness was associated with more severe or frequent experiences of these outcomes, with participants that demonstrated a preference for eveningness more likely to report poorer affective functioning and increased psychological distress. Mediation analysis found the relationship between chronotype and these outcome measures was completely or partially mediated by insomnia symptom severity measured by the validated Sleep Condition Indicator insomnia scale. Taken together, these findings add further evidence for the negative consequences of increased eveningness. Additionally, our results show that chronotype and sleep disturbances should be considered when assessing mental well-being. Implementing appropriate sleep-related behavior change or schedule alterations can offer a tool for mitigation or prevention of psychological distress in students that report a preference for later sleep and wake times.
... Around 35% of the general population are evening types [32], who are particularly vulnerable to disruption of sleep and higher social jetlag. This is due to a chronic and recurrent mismatch between the internal circadian system, sleep-wake behavior, and social schedules, which impacts physical and cognitive performance, general health, and wellbeing [14,33]. Our results also show that all of these factors (later mid-sleep, higher social jetlag, and longer sleep latency) are associated with poorer mental health outcomes. ...
... The finding that these factors are more pronounced in definite evening types highlights a critical need to account for individual differences when managing athletes through changes to schedules. This could include increasing flexibility and using circadian interventions to shift circadian timing [33]. ...
Article
Full-text available
The global coronavirus 19 (COVID-19) pandemic and associated lockdown restrictions resulted in the majority of sports competitions around the world being put on hold. This includes the National Basketball Association, the UEFA Champions League, Australian Football League, the Tokyo 2020 Olympic Games, and regional competitions. The mitigation strategies in place to control the pandemic have caused disruption to daily schedules, working environments, and lifestyle factors. Athletes rely on regular access to training facilities, practitioners, and coaches to maintain physical and mental health to achieve maximal performance and optimal recovery. Furthermore, participation in sport at any level increases social engagement and promotes better mental health. It is, therefore, critical to understanding how the COVID-19 pandemic and associated lockdown measures have affected the lives of athletes. We surveyed elite and sub-elite athletes (n = 565) across multiple sports. Significant disruptions were reported for all lifestyle factors including social interactions, physical activity, sleep patterns, and mental health. We found a significant increase in total sleep time and sleep latency, as well as a delay in mid-sleep times and a decrease in social jetlag. Training frequency and duration significantly decreased. Importantly, the changes to training and sleep-related factors were associated with mental health outcomes. With spikes in COVID-19 cases rising around the world and governments reinstituting lockdowns (e.g. United Kingdom; Melbourne, Australia; California, USA) these results will inform messaging and strategies to better manage sleep and mental health in a population for whom optimal performance is critical.
... • The Horne-Östberg (HÖ) questionnaire, which defines chronotype as definitely morning (score 70-86), moderately morning (59-69), intermediate (42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58), moderately evening (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41), and definitely evening (16-30) based on 19 self-administered questions aimed at identifying preferred time of day for carrying out certain activities [24,25]. ...
... Of course, in this instance we treated young healthy adults of an age when: i) the retinalhypothalamic-pineal tract is expected to be unimpaired in anatomy and physiology; ii) features of delayed sleep phase disorder are still fairly common, especially in males, and iii) poor light-dark hygiene is also common, in relation to the widespread use of light emitting devices such as computers, tablets and smart-phones in the evening and night hours. The light that comes from such devices is relatively strong and blue-enriched, thus the short-wavelength filter glasses might have been particularly useful [44,45]. It would be interesting, in future studies, to test short-wavelength filter glasses as a stand-alone, as the effects observed in this study might depend on either device, or their combination. ...
Article
Full-text available
Chronobiology is not routinely taught to biology or medical students in most European countries. Here we present the results of the chronobiology practicals of a group of students of the University of Padova, with a view to highlight some interesting features of this group, and to share a potentially interesting cross-faculty teaching experience. Thirty-eight students (17 males; 22.9 ± 1.6 yrs) completed a set of self-administered electronic sleep quality [Pittsburgh Sleep Quality Index (PSQI)], chronotype and sleepiness [Epworth Sleepiness Scale (ESS)] questionnaires. They then went on to complete sleep diaries for two weeks. Sixteen also wore an actigraph, 8 wore wireless sensors for skin temperature, and 8 underwent a course of chronotherapy aimed at anticipating their sleep-wake timing. Analyses were performed as practicals, together with the students. Average PSQI score was 5.4 ± 1.9, with 15 (39%) students being poor sleepers. Average ESS score was 6.5 ± 3.3, with 3 (8%) students exhibiting excessive daytime sleepiness. Seven classified themselves as definitely/moderately morning, 25 as intermediates, 6 as moderately/definitely evening. Students went to bed/fell asleep significantly later on weekends, it took them less to fall asleep and they woke up/got up significantly later. Diary-reported sleep onset time coincided with the expected decrease in proximal skin temperature. Finally, during chronotherapy they took significantly less time to fall asleep. In conclusion, significant abnormalities in the sleep-wake patterns of a small group of university students were observed, and the students seemed to benefit from chronotherapy. We had a positive impression of our teaching experience, and the chronobiology courses obtained excellent student feedback.
... Chronotype is a product of both genetics and environment (Facer-Childs, Middleton, Skene, & Bagshaw, 2019;Hu et al., 2016;Lane et al., 2016), and is expressed as diurnal variations in characteristics such as energy levels, affect, and both cognitive and physical performance (Facer-Childs, Boiling, & Balanos, 2018;Goldstein, Hahn, Hasher, Wiprzycka, & Zelazo, 2007;Merrow, Spoelstra, & Roenneberg, 2005;Miller et al., 2015). ...
... However, research on insomnia's effect on subsequent mood and mental health outcomes (e.g., Bernert, Hom, Iwata, & Joiner, 2017;Littlewood et al., 2019) combined with research on chronotype's causal association with poor sleep quality points towards a directional chronotype-insomnia-affect pathway (Bakotic et al., 2017;Facer-Childs et al., 2019;Konjarski, Murray, Lee, & Jackson, 2018). This putative causal relationship is supported by the results of the present study. ...
Preprint
Full-text available
Chronotype describes a person's general preference for mornings, evenings or neither. It is typically conceptualized as a continuous unidimensional spectrum from morningness to eveningness. Eveningness is associated with poorer outcomes across a myriad of physical and mental health outcomes. This preference for later sleep and wake times is associated with increased risk of depression, anxiety, and suicidal ideation and behaviors in both clinical and community samples. However, the mechanisms underlying the negative consequences of this preference for evenings is not fully understood. Previous research has found that sleep disturbances may act as a mediator of this relationship. The present study aimed to explore the associations between chronotype and affective outcomes in a community sample of young adults. Additionally, it aimed to investigate the potential role of insomnia as a mediator within these relationships. Participants (n = 260) completed an anonymous self-report survey of validated measures online which assessed chronotype, insomnia symptoms, and a range of affective outcomes (defeat, entrapment, stress, suicide risk, and depressive and anxious symptomology). Eveningness was associated with more severe or frequent experiences of these outcomes, with young adults demonstrating a preference for eveningness more likely to report poorer affective functioning and increased psychological distress. Mediation analysis found the relationship between chronotype and these outcome measures were partially mediated by sleep disturbances as measured by the well-validated Sleep Condition Indicator insomnia scale. Taken together, these findings add further evidence for the negative consequences of increased eveningness. Additionally, our results show that chronotype and sleep disturbances should be considered when assessing mental well-being. Implementing appropriate sleep-related behavior change or schedule alterations can offer a tool for mitigation or prevention psychological distress in young adults who report a preference for later sleep and wake times.
... Extreme preferences are morningness and eveningness. The individual preference of daily cycle is set up by a combination of genetic and epigenetic factors and has influence on physical and mental health [8,9]. For example, cortisol levels differ in two chronotypes (early and late). ...
... There were significant reductions in subjective ratings of depression and stress. In addition, elements of cognitive (reaction time) and physical (grip strength) performance were significantly improved during 'non optimal' times [8]. There is another new approach to chrono-medicine [105]. ...
Article
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This review aims to summarize the knowledge about the relationship between circadian rhythms and their influence on the development of type 2 diabetes mellitus (T2DM) and metabolic syndrome. Circadian rhythms are controlled by internal molecular feedback loops that synchronize the organism with the external environment. These loops are affected by genetic and epigenetic factors. Genetic factors include polymorphisms and mutations of circadian genes. The expression of circadian genes is regulated by epigenetic mechanisms that change from prenatal development to old age. Epigenetic modifications are influenced by the external environment. Most of these modifications are affected by our own life style. Irregular circadian rhythm and low quality of sleep have been shown to increase the risk of developing T2DM and other metabolic disorders. Here, we attempt to provide a wide description of mutual relationships between epigenetic regulation, circadian rhythm, aging process and highlight new evidences that show possible therapeutic advance in the field of chrono-medicine which will be more important in the upcoming years.
... In some cases, light exposure can represent the primary or secondary outcome of a specific clinical trial, such as in studies attempting to modify lifestyle to alter light exposure and visual behavior in myopia control (e.g., Ref. 30 ), or studies aimed to optimize light exposure in order to support sleep and/or daytime functioning (e.g., Ref. 59 ). In these studies, personalized light exposure is the study outcome, and therefore measurements need to be sensitive enough to capture change in light patterns in response to the trial intervention. ...
Article
Full-text available
Background Light exposure is an important driver and modulator of human physiology, behavior and overall health, including the biological clock, sleep-wake cycles, mood and alertness. Light can also be used as a directed intervention, e.g., in the form of light therapy in seasonal affective disorder (SAD), jetlag prevention and treatment, or to treat circadian disorders. Recently, a system of quantities and units related to the physiological effects of light was standardized by the International Commission on Illumination (CIE S 026/E:2018). At the same time, biometric monitoring technologies (BioMeTs) to capture personalized light exposure were developed. However, because there are currently no standard approaches to evaluate the digital dosimeters, the need to provide a firm framework for the characterization, calibration, and reporting for these digital sensors is urgent. Objective This article provides such a framework by applying the principles of verification, analytic validation and clinical validation (V3) as a state-of-the-art approach for tools and standards in digital medicine to light dosimetry. Results This article describes opportunities for the use of digital dosimeters for basic research, for monitoring light exposure, and for measuring adherence in both clinical and non-clinical populations to light-based interventions in clinical trials.
... Thus, factors including light exposure, work hours, eating habits, physical activity and medication use affect the body according to individual traits/states, such as genome, age, gender, ethnicity and chronotype (Table 1). Circadian hygiene strategies have been shown to be successful in studies that simulate real-life conditions [6]. The temporal flexibility of society would allow such strategies to be adopted more easily. ...
Article
Full-text available
Circadian hygiene, a concept not to be confused with the notion of public or social hygiene, should be discussed among experts and society. Light–dark cycles and other possible synchronizers of the human circadian timing system affect ways of life, including sleeping, eating, working and physical activity. Some of these behaviors have also been investigated individually as synchronizers (e.g., eating times). Therefore, the knowledge held today about circadian rhythms, and their implications for health, allows future perspectives in this field to be mapped. The present article summarizes the latest knowledge on factors influencing circadian rhythms to discuss a perspective for the future of health promotion based on circadian hygiene. However, it is important to highlight that circadian hygiene is the product of an imbrication of individual and societal involvement. First, it is important to adopt practices and devise public health policies in line with circadian hygiene. Second, individual healthy habits require internal rhythms to be examined. Last, the research agenda on circadian hygiene can be developed on a public as well as individual level, raising the question as to how much society is willing to embrace this change.
... From these observations arises the question on whether the evening chronotype can be considered a form of SJL. And the answer is most probably 'no' as although chronotype is a state of phase of entrainment reflecting the continuous adaptations of circadian system to zeitgeber changes [66,67], it also has a genetic basis [68]. SJL is a metric describing the chronic misalignment between the circadian system and social schedules, results from sleep timing variability between weekdays and weekends and includes a component of sleep debt that may influence associated health risks [64]. ...
Article
Full-text available
The objective of this scoping review was to summarize previous studies which examined the effect of day-to-day variability in sleep timing and social jetlag (SJL) on dietary intake. A systematic literature search was conducted in PubMed, Embase, and Clarivate Analytics Web of Science and we identified 22 records. No difference in caloric and macronutrient intake between SJL groups was observed in studies that enrolled healthy young adults. However, studies that enrolled participants with obesity and obesity-related chronic conditions reported a higher caloric intake and a higher intake of carbohydrates, total fat, saturated fats, and cholesterol in participants with SJL than in those without. Most studies reported a lower quality of diet, a delayed mealtime, and eating jetlag in participants with SJL vs. those without SJL. No correlation of day-to-day variability in sleep timing with average caloric intake was observed, but bed-time variability was negatively associated with diet quality. Methodological issues have been identified in sources assessed including study design, power calculation, population enrolled, and tools/metrics used for sleep timing variability assessment. Future well powered longitudinal studies, with clear protocols, standardized metrics, including all age groups from general population are needed to clarify the dietary intake consequences of variability in sleep timing.
... Studies have shown that managing employee health at work can improve employee performance and the company's performance. This issue is becoming more prevalent globally [26][27][28]. ...
Article
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Background: Breakfast is the most important meal of the day and has been associated with longevity. Regular breakfast consumers often have a healthy lifestyle, including a healthy diet and regular physical activity. Methods: We examined the association between breakfast type, chronotype (morningness-eveningness), and physical activity in 3395 Japanese workers using a cross-sectional web survey. Results: Participants who ate Japanese breakfasts showed an early chronotype, while those who ate breakfast cereal exhibited a later chronotype. Physical activity was positively associated with adopting a Japanese breakfast style. Japanese breakfast eaters performed physical activities from 6:00-9:00 compared with other breakfast eaters. Conclusion: Our findings suggest that eating a Japanese breakfast is associated with an earlier chronotype (morningness) and higher physical activity.
... Mendelian randomization results from several studies confirm a causal effect of the 'lifelong intervention' of genetic variation for morning chronotype as protective for psychiatric disorders, especially major depressive disorder [31][32][33]134,135 . A recent randomized control trial that targeted sleep timing, meal timing, light exposure, caffeine intake, napping behaviour and exercise behaviour provided evidence for the feasibility of interventions to produce clinically relevant shifts in circadian rhythms 136 . In recent studies of insomnia and short sleep, a causal link to coronary artery disease and myocardial infarction was demonstrated [114][115][116][117] , further supporting numerous observational studies linking insomnia with cardiac outcomes 137,138 . ...
Article
Circadian rhythms and sleep are fundamental biological processes integral to human health. Their disruption is associated with detrimental physiological consequences, including cognitive, metabolic, cardiovascular and immunological dysfunctions. Yet many of the molecular underpinnings of sleep regulation in health and disease have remained elusive. Given the moderate heritability of circadian and sleep traits, genetics offers an opportunity that complements insights from model organism studies to advance our fundamental molecular understanding of human circadian and sleep physiology and linked chronic disease biology. Here, we review recent discoveries of the genetics of circadian and sleep physiology and disorders with a focus on those that reveal causal contributions to complex diseases. The circadian system and sleep physiology are linked to myriad biological processes, the disruption of which is detrimental to human health. Here, the authors review insights from genetic studies of human circadian and sleep phenotypes and disorders, with a focus on those with causal contributions to other complex diseases.
... Chronotype (i.e., an evening preference) is suggested to be moderately modifiable (Leocadio-Miguel et al. 2021). Nevertheless, some interventions targeting light exposure, fixed meals times, caffeine intake and exercise may induce a phase advance in individuals with late chronotypes, (Facer-Childs et al. 2019;Thomas et al. 2020). Such an effect has not been explored yet in a population with BD. ...
Article
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Background Life expectancy is significantly decreased in bipolar disorder (BD). This is associated with accelerated cellular aging which can be estimated by telomere length (TL). However, specific determinants of shorter TL in BD are under-explored. This study examines whether circadian misalignment (i.e. mismatch between preferred and actual phase of circadian activity rhythms) is associated with shorter TL in BD. Methods Euthymic individuals with BD (n = 101) undertook 21 consecutive days of actigraphy recording and completed the Composite Scale of Morningness (CSM) to assess phase preference for activities (chronotype). Polymerase chain reaction was used to measure TL in blood. Cluster analysis identified circadian aligned/misaligned subgroups as defined by preferred (CSM score) and actual phases of activity (actigraphically determined onset of active and inactive periods). We tested for any associations between TL and clusters, with adjustments for between-cluster differences in socio-demographic and illness factors. Results We identified three clusters: an "Aligned Morning" cluster (n = 31) with preferred and actual timing of activity in the morning, an "Aligned Evening" cluster (n = 37) with preferred and actual timing of activity in the evening and a "Misaligned" cluster (n = 32) with an evening chronotype, but an earlier objective onset of active periods. After adjustment for confounders, we found that TL was significantly associated with circadian misalignment and older age. Conclusions Circadian misalignment may partly explain shorter TL in BD and could contribute to accelerated aging in these individuals.
... Two alternative sets of advice (novel in their formulation but grounded in circadian practice; Abbott et al., 2015) were provided (and remained the same on every subsequent "refresh" monthly reminder) with comparable expected benefits (i.e., balancing out because the first type of advice was slightly less prescriptive but probably easier to follow, and the second slightly more prescriptive but probably more difficult to follow) exerted via two different forms of habits' adjustment (Facer-Childs et al., 2019). Both included elements of the recommendations routinely provided to patients with either a formal diagnosis and/or features of delayed sleep phase type (Abbott et al., 2015), which is common in adolescents and young adults. ...
Article
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The aims of the present study were to obtain sleep quality and sleep timing information in a group of university students and to evaluate the effects of a circadian hygiene education initiative. All students of the University of Padova (approximately 64,000) were contacted by e-mail (major campaigns in October 2019 and October 2020) and directed to an ad hoc website for collection of demographics and sleep quality/timing information. Participants (n = 5,740) received one of two sets of circadian hygiene advice (“A regular life” or “Bright days and dark nights”). Every month, they were then asked how easy it had been to comply and provided with the advice again. At any even month from joining, they completed the sleep quality/timing questionnaires again. Information on academic performance was obtained post hoc, together with representative samples of lecture (n = 5,972) and examination (n = 1,800) timings, plus lecture attendances (n = 25,302). Fifty-two percent of students had poor sleep quality, and 82% showed signs of social jetlag. Those who joined in October 2020, after several months of lockdown and distance learning, had better sleep quality, less social jetlag, and later sleep habits. Over approximately a year, the “Bright days and dark nights” advice resulted in significantly earlier get-up times compared with the “A regular life” advice. Similarly, it also resulted in a trend toward earlier midsleep (i.e., the midpoint, expressed as clock time, between sleep onset and sleep offset) and toward a decrease in the latency between wake-up and get-up time, with no impact on sleep duration. Significant changes in most sleep quality and sleep timing variables (i.e., fewer night awakenings, less social jetlag, and delayed sleep timing during lock-down) were observed in both advice groups over approximately a year, mostly in association with pandemic-related events characterizing 2020. Early chronotype students had better academic performances compared with their later chronotype counterparts. In a multivariate model, sleep quality, chronotype and study subject (science and technology, health and medical, or social and humanities) were independent predictors of academic performance. Taken together, these results underlie the importance of designing circadian-friendly university timetables.
... Two alternative sets of advice (novel in their formulation but grounded in circadian practice; Abbot et al., 2015) were provided (and remained the same on every subsequent "refresh" monthly reminder) with similar, expected effects exerted via two different forms of habits' adjustment (Facer-Childs et al., 2019). Both included elements of the recommendations routinely provided to patients with either a formal diagnosis and/or features of delayed sleep phase type (Abbot et al., 2015), which is common in adolescents and young adults. ...
Preprint
The aims of the present study were to obtain sleep quality and sleep timing information in a group of university students, and to evaluate the effects of a circadian hygiene education initiative. All students of the University of Padova (approximately 64,000) were contacted by e-mail (major campaigns in October 2019 and October 2020) and directed to an ad hoc website for collection of demographics and sleep quality/timing information. Participants (n=5740) received one of two sets of circadian hygiene advice ('A regular life' or 'Bright days and dark nights'). Every month, they were then asked how easy it had been to comply, and provided with the advice again. At any even month from joining, they completed the sleep quality/timing questionnaires again. Information on academic performance was obtained post hoc, together with representative samples of lecture (n=5972) and exam (n=1800) timings, plus lecture attendances (n=25,302). 52% of students had poor sleep quality and 82% showed signs of sleep deprivation. Those who joined in October 2020, after several months of lockdown and distance learning, had better sleep quality, less sleep deprivation and later sleep habits. The 'Bright days and dark nights' advice resulted in earlier get-up time/midsleep compared to the 'A regular life' advice. Significant changes in most sleep quality and sleep timing variables were observed in both advice groups over time, also in relation to pandemic-related events characterising 2020. Early-chronotype students had better academic performances compared to their later chronotype counterparts. In a multivariate model, sleep quality, chronotype and study subject were independent predictors of academic performance. Taken together, these results underlie the importance of designing circadian-friendly university timetables.
... Several circadian-related characteristics and behaviours may account for different susceptibilities to mental disorders. Accordingly, the individual timing preference (chronotype) is associated with a higher rate of various mental disorders including seasonal and bipolar depression [70][71][72]. In addition, inappropriate exposure to light due to social schedules, such as shift work and jetlag, demonstrably affects the circadian rhythms and consequently increases the susceptibility to mental disorders [73][74][75]. ...
Conference Paper
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This article provides a brief description of some of the most remarkable sessions of the @EuroRespSoc Lung Science Conference and the Sleep and Breathing Conference 2021 and presents the new incoming members of the ECMC (@EarlyCareerERS) https://bit.ly/2RSDP40.
... Health management of employees in the workplace is shown to have improved their performance (that is, leading to a reduction in absenteeism and an increase in presenteeism) as well as overall corporate performance. This strategy is now receiving attention worldwide [1][2][3]. However, the protocol for health management is under development and needs to be verified with scientific evidence [4]. ...
Article
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Breakfast skipping and nighttime snacking have been identified as risk factors for obesity, diabetes, and cardiovascular diseases. However, the effects of irregularity of meal timing on health and daily quality of life are still unclear. In this study, a web-based self-administered questionnaire survey was conducted involving 4490 workers (73.3% males; average age = 47.4 ± 0.1 years) in Japan to investigate the association between meal habits, health, and social relationships. This study identified that irregular meal timing was correlated with higher neuroticism (one of the Big Five personality traits), lower physical activity levels, and higher productivity loss. Irregular meal timing was also associated with a higher incidence of sleep problems and lower subjective health conditions. Among health outcomes, a high correlation of irregular meal timing with mental health factors was observed. This study showed that irregularity of meal timing can be explained by unbalanced diets, frequent breakfast skipping, increased snacking frequency, and insufficient latency from the last meal to sleep onset. Finally, logistic regression analysis was conducted, and a significant contribution of meal timing irregularity to subjective mental health was found under adjustment for other confounding factors. These results suggest that irregular meal timing is a good marker of subjective mental health issues.
... Circadian rhythms influence our behaviour and status of health in profound ways. Maintaining a regular sleep-wake rhythm is clearly beneficial both in disease prevention [14][15][16] and better disease management 8 . A synchronization of the activity and sleep periods according to the endogenous circadian rhythms optimize sleep 17 , cognitive processing 18 , metabolic functions 19 , immune functions 2 and mood 20 . ...
Article
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The individual variation in the circadian rhythms at the physiological level is not well understood. Albeit self-reported circadian preference profiles have been consolidated, their premises are grounded on human experience, not on physiology. We used data-driven, unsupervised time series modelling to characterize distinct profiles of the circadian rhythm measured from skin surface temperature in free-living conditions. We demonstrate the existence of three distinct clusters of individuals which differed in their circadian temperature profiles. The cluster with the highest temperature amplitude and the lowest midline estimating statistic of rhythm, or rhythm-adjusted mean, had the most regular and early-timed sleep–wake rhythm, and was the least probable for those with a concurrent delayed sleep phase, or eveningness chronotype. While the clusters associated with the observed sleep and circadian preference patterns, the entirely unsupervised modelling of physiological data provides a novel basis for modelling and understanding the human circadian functions in free-living conditions.
... On the other hand, recent experiments have clearly shown that the delayed circadian phase of E-types can be phase advanced by exposure to a proper lighting regime and daily routine. This intervention can significantly improve E-types' cognitive and physical performance (Facer-Childs et al. 2019a). Thus, the strategy to align the overall performance capacity between extreme chronotypes is in strict adherence to daily routine and exposure to the morning light. ...
Article
Circadian clocks regulate multiple physiological domains from molecular to behavioral levels and adjust bodily physiology to seasonal changes in day length. Circadian regulation of cellular bioenergy and immunity in the cardiovascular and muscle systems may underpin the individual diurnal differences in performance capacity during exercise. Several studies have shown diurnal differences in cardiopulmonary parameters at maximal and submaximal workloads in morning and evening circadian human phenotypes. However, the effect of seasons on these changes was not elucidated. In this study, we recruited subjects with Morningness–Eveningness Questionnaire scores corresponding to morning and evening types. Subjects underwent morning (7:00–9:00) and evening (20:00–22:00) maximal workload spiroergometry in both winter and summer seasons. We analyzed their performance time, anaerobic threshold, heart rate, and respiratory parameters. Our results suggest that evening types manifest diurnal variations in physical performance, particularly in winter. They also have slower heart rate recovery than morning types, irrespective of the time of day or season. Compared to winter, the chronotype effect on the magnitude of morning–evening differences in performance time, maximal heart rate, and anaerobic threshold onset was more significant in summer. Our data are in concordance with previous observations and confirm the difference between morning and evening types in the timing of maximum performance capacity.
... Recent research (Facer-Childs et al. 2019) shows that sleep timing patterns can be reset with beneficial effects, and positive interventions can be done in people's homes during social distancing (Facer-Childs et al. 2020). Co-author Schmid (2020) has identified seven daily bodily phases associated with the circadian rhythm, based on chronobiological research and workshops conducted with a wide range of participants. ...
Article
‘Uchronian Critical Mass’ exploits the historical opportunity the COVID-19 pandemic and resulting quarantines have opened up to question societal time systems, which can conflict with natural rhythms, leading to adverse effects on mental and physical health. We describe an experiment in which participants step outside societal time, choose their own time-giver and live by it for up to one week. As an experiment in artistic research grounded in science, we specifically enlisted fellow artists and asked them to document their experiment using any chosen means. The results included unexpected social and spiritual qualities, evidenced increased concentration and productivity, and drew attention to aspects of societal time generally taken for granted by introducing non-linear temporal elements. The experiment impacted each artist’s working practices and subsequent work. Collectively, the results show the potential of artistic practice to influence a broader questioning of societal time through multisensory means, highlighting the unique role artists hold as outsiders to lead the way in forming creative approaches to social and political issues.
... However, this effect lasted only 1 week out of 4 in the study and was present in only half of the volunteers. Facer-Childs et al. (2019) in an elegant intervention experiment in which hours of light exposure, diet and exercise, caffeine intake, and napping of evening individuals were controlled showed a significant phase advance in DLMO and cortisol acrophase of nearly 2 h. ...
Article
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Inter-individual differences have been described in circadian timing organization, including the characteristics of phase preferences known as chronotypes. Social, biological and geophysical factors can influence the characteristics of morning-evening preference. Although morning individuals report inability to return to sleep after waking up and difficulties in maintaining nocturnal sleep most complaints are reported by evening individuals. The objective of the present study was to analyze the temporal organization of chronotypes at different phases. We measured the rhythms of activity/rest, sleep/wake, wrist temperature, attention and cycles of exposure to light of 32 university volunteers over 21 consecutive days of data collection. The acrophases of the analyzed rhythms correlate with the score of Horne & Östberg Questionnaire, but not the parameters of the cycle of exposure to light. The evening type volunteers who have morning classes showed no corresponding phase advanced of the rhythms, social jet lag and disruption in the rhythm of attention, suggesting difficulty to entrainment by the university schedules.
... Another unresolved matter concerns who can be diagnosed. Some reserve this for night workers only (Rajaratnam et al., 2011), whereas others argue that SWD may even affect day workers (Flo et al., 2012), as it is conceivable that night owls, for example, having day work with an early start, will work at a time overlapping with their usual sleep time (Facer-Childs et al., 2019). These factors may impact the estimated prevalences of SWD. ...
Article
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Objectives: No systematic review or meta-analysis concerning the prevalence of shift work disorder (SWD) has been conducted so far. The aim was thus to review prevalence studies of SWD, to calculate an overall prevalence by a random effects meta-analysis approach and investigate correlates of SWD prevalence using a random-effects meta-regression. Methods: Systematic searches were conducted in ISI Web of Science, PsycNET, PubMed, and Google Scholar using the search terms “shift work disorder” and “shift work sleep disorder.” No restrictions in terms of time frame were used. Included studies had to present original data on the prevalence of SWD in an occupational sample published in English. A total of 349 unique hits were made. In all, 29 studies were finally included from which two authors independently extracted data using predefined data fields. The meta-regression included four predictors (diagnostic criteria, study country, type of workers, and sample size). Results: The overall prevalence of SWD was 26.5% (95% confidence interval = 21.0–32.8). Cochran Q was 1,845.4 ( df = 28, p < 0.001), and the I ² was 98.5%, indicating very high heterogeneity across the observed prevalence estimates. Diagnostic criteria (International Classification of Sleep Disorders-2 = 0, International Classification of Sleep Disorders-3 = 1) and sample size were inversely related to SWD prevalence. Conclusions: The prevalence of SWD was high across the included studies. The between-study disparity was large and was partly explained by diagnostic criteria and sample size. In order to facilitate comparative research on SWD, there is a need for validation and standardization of assessment methodology as well as agreement in terms of sample restrictions.
... This is despite the fact that they are known to account for variability in behavioural performance and rs-FC (Facer-Childs et al., 2019a;Tian et al., 2019). In addition, people with a late circadian phenotype (LCP) are at risk of circadian misalignment and sleep restriction when forced to adhere to the societal day (Facer-Childs et al., 2019b), which is also known to impact on rs-FC (Khalsa et al., 2016). ...
Article
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Background Functional connectivity (FC) of the motor network (MN) is often used to investigate how intrinsic properties of the brain are associated with motor abilities and performance. In addition, the MN is a key feature in clinical work to map the recovery after stroke and aid the understanding of neurodegenerative disorders. Time of day variation and individual differences in circadian timing, however, have not yet been considered collectively when looking at FC. Methods A total of 33 healthy, right handed individuals (13 male, 23.1 ± 4.2 years) took part in the study. Actigraphy, sleep diaries and circadian phase markers (dim light melatonin onset and cortisol awakening response) were used to determine early (ECP, n =13) and late (LCP, n = 20) circadian phenotype groups. Resting state functional MRI testing sessions were conducted at 14:00 h, 20:00 h and 08:00 h and preceded by a maximum voluntary contraction test for isometric grip strength to measure motor performance. Results Significant differences in FC of the MN between ECPs and LCPs were found, as well as significant variations between different times of day. A higher amplitude in diurnal variation of FC and performance was observed in LCPs compared to ECPs, with the morning being most significantly affected. Overall, lower FC was significantly associated with poorer motor performance. Discussion Our findings uncover intrinsic differences between times of day and circadian phenotype groups. This suggests that central mechanisms contribute to diurnal variation in motor performance and the functional integrity of the MN at rest influences the ability to perform in a motor task.
... The utilization of a rotating schedule of surgical teams coupled to a dedicated emergency OR room would likely facilitate more prompt surgical intervention and decrease length of stay. With the rapidly increasing number of outpatient surgeries being performed, and rising surgical demand due to COVID-19 limitations, 11 developing an effective infrastructure for after-hours surgery could have tremendous benefits for both physicians and patients alike. ...
Article
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After-hours surgery represents a novel solution that can effectively combat surgical fatigue of care teams in addition to addressing the high volume of surgical backlog associated with the repercussions of the COVID-19 pandemic. This commentary seeks to rationalize how successful employment of a dedicated after-hours surgical team and protocol has tremendous potential for increased efficiency while maintaining good surgical outcomes in patients.
... An elite athlete will have some insight or feeling into daily variations of when they feel or perform their best. However, with research-based evidence and expert consultants, an athlete can consider interventions to shift the timing of their biological rhythms to try and optimise performance (Facer-Childs et al., 2019b). Research now demonstrates that there is a point in the day an athlete is likely to be achieving peak performance, based on circadian phenotype and time since entrained wake (Facer-Childs and Brandstaetter, 2015a). ...
Article
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Timing is everything. It allows us to anticipate the best time to conserve energy, identify the time of peak performance, recognise when attention may be sub-optimal, and find the most effective time for nutritional intake. The study of timing and cyclic phenomena in humans is termed human chronobiology (chrono= time) and has many implications for the elite athlete.
... Further detrimental effects on the mental and somatic health of the late chronotype have been described in terms of its association with certain personal dispositions (e.g., impulsivity) or habits (e.g., sedentary lifestyle, smoking, and other substance abuse) (Kandeger et al. 2019;Patterson et al. 2016;Shimura et al. 2018). Such findings underline the need to investigate evening chronotype as a diagnostic, prognostic, and possibly therapeutic factor in psychological and somatic disorders (Facer-Childs et al. 2019;Kivelä et al. 2018) Suicide is considered to be the most deleterious consequence of poor mental health, with a global mortality rate of 10.5 per 100,000 population in 2016 (World Health Organization 2019). Despite displaying an apparent downward trend in mortality (from 12.9 per 100,000 in 2000) it remains a major clinical issue, particularly among the younger population, aged 15 to 29 y of age, among whom suicide is the second-leading cause of death (World Health Organization 2019). ...
Article
The aim of the present study was to evaluate whether anxiety and insomnia symptoms, somatic symptoms, and social dysfunction mediate the link between chronotype and suicidality, as depressive symptoms are known to do, among students of the faculties of Medicine and Psychology. Data from a total of 289 students were eligible for the analysis. The students completed the Suicide Behaviors Questionnaire – Revised, Composite Scale of Morningness, General Health Questionnaire. Single-predictor linear regression models were created to predict suicidality, with a subsequent mediation analysis. A preference toward eveningness was associated with an increase in suicidality Somatic symptoms, anxiety/insomnia, and depressive symptoms fully mediated the relationship between chronotype and suicidality. Depressive symptoms were found to present the strongest effect size of mediation. Social dysfunction was associated with both eveningness and suicidality, but did not play a mediating role. There might be a need to evaluate nonpsychotic mental health indices other than depressive symptoms when assessing the link between suicidality and chronotype among students of the faculties of Medicine and Psychology.
... A difference was identified between these two groups even in decision-making tasks, where only a 3-hour phase difference in molecular clockwork was sufficient to influence the decision-making, highlighting the effects of endogenous clock function in human performance [16]. Chronotype influences both physical and mental health [18,19] with cortisol levels also being different in early and late hours preferring people. Early chronotype presents with a more pronounced adrenocortical activation after waking up compared to the late chronotype [14]. ...
Article
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Sleep plays an important role in maintaining brain function, memory consolidation, hormonal balance, immune system function, growth, and repair. The physiological and psychological effects of disruptions in sleep highlight its importance in human health and wellness. Epigenetic roles are proposed in sleep, and circadian regulation, but only a limited number of studies have determined the mechanism that underlies the epigenetics of environmental factors interacting with the sleep, particularly the ones related to sleep disruption. Therefore, studying epigenetics of sleep and sleep disorders can help elucidate the way these factors promote or inhibit sleep disorders, potentially guiding the development of precision medicines or preventive strategies. However, before discovering useful epigenetic-based interventions for sleep disorders, we need to overcome many challenges. As a relatively new field, there are unmet needs that call for further investigation of epigenetic mechanisms underlying sleep disruption. This review focuses on the current status of epigenetic mechanisms in sleep disruption (e.g., sleep deprivation and circadian dysregulation), which highlights a great potential of both animal and human studies to explain the disturbances in sleep, associated consequences, and novel therapeutic potentials. Translating the epigenetic research in sleep disturbances can eventually lead to better diagnosis, prognosis, prevention, and therapy in the clinics.
... Paradoxically sleep/wake patterns, however, were found to have greater variability in the group that did not have electricity at home. The timing of the DLMO, the most commonly used and reliable marker of circadian phase, has been shown to positively correlate with the timing of midsleep on free days (MSFsc) (Wright et al., 2013;Kantermann and Burgess, 2017;Facer-Childs et al., 2019). This MSFsc measure is calculated from the Munich ChronoType Questionnaire (MCTQ) (Roenneberg et al., 2003). ...
Article
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The response to a zeitgeber, particularly the light/dark cycle, may vary phenotypically. Phenotypic plasticity can be defined as the ability of one genome to express different phenotypes in response to environmental variation. In this opinion paper, we present some evidence that one of the most prominent effects of the introduction of electric light to the everyday life of humans is a significant increase in phenotypic plasticity and differences in interindividual phases of entrainment. We propose that the healthy limits of phenotypic plasticity have been surpassed in contemporary society.
... In this view, reducing social jetlag could become a goal for bariatric patients and be added to the multiple factors associated with weight loss in these individuals. The literature shows that sleep hygiene [50,51], such as the guidelines for going to sleep earlier, controlling exposure to light at night [52] and light treatment for shift workers [53], is efficient for the circadian alignment of individuals. In addition, given the potential synchronisation of nutrients and meals, topics such as "when to eat" and not just "what to eat" should emerge and be part of the nutritional approach of bariatric patients, where the predominant food intake occurs during the day, and excessive food intake at night is avoided [54][55][56]. ...
Article
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Purpose: Circadian misalignment has been associated with an increased risk of overweight and obesity, as well as changes in metabolic parameters. This study evaluated the association between social jet lag (SJL), a measure of circadian misalignment, and anthropometric, metabolic and food intake outcomes 6 months after bariatric surgery. Materials and methods: A total of 122 bariatric patients were included (77% female, aged 33 years (range 28-41); 79.5% underwent Roux-en-Y gastric bypass). Anthropometric, food consumption and SJL were evaluated in the preoperative evaluation and in the third and sixth months after surgery. SJL was calculated based on the absolute difference between the mid-sleep time on weekends and weekdays. Generalised estimating equations and linear regression were performed to evaluate the associations between mean SJL exposure and the outcomes. Results: The interaction between SJL and follow-up time negatively influenced the evolution of weight (p = 0.01), BMI (p = 0.04) and insulin levels (p = 0.01). SJL had an effect on intake of calories (p = 0.001), carbohydrate (p = 0.005) and total (p = 0.007), monounsaturated (p = 0.03) and polyunsaturated fat (p < 0.001). Linear regression showed a negative association between mean SJL exposure over the 6 months and the percentage of weight loss (coefficient = - 0.30, p = 0.006), body weight loss (kg) (coefficient = - 0.17, p = 0.03) and the reduction of BMI (coefficient = - 0.24, p = 0.007). Conclusions: SJL was negatively associated with anthropometric, metabolic and food consumption outcomes 6 months after bariatric surgery. Future studies with longer follow-up are needed to confirm these findings. Trial registration: Clinical Trials.gov : NCT03485352.
Article
Background: Poor sleepers have a higher prevalence of mental health problems, and vice versa. However, the mechanisms underlying this association remain unknown. We aimed to examine the bidirectional association between sleep quality and mental health, and further explore the moderating effects of PER3 gene DNA methylation on the association. Methods: This prospective longitudinal study was conducted from April 2019 to May 2021, integrated questionnaire and blood sample data from 2 universities in Anhui and Jiangxi Provinces. The current study recruited 1179 young adults at baseline and conducted the follow-up survey among 1135 half a year later. The sleep quality and depressive symptoms, anxiety symptoms, and stress symptoms were assessed using a questionnaire at baseline and follow-up. Blood samples were collected at baseline, and MethyTarget™ was used to detect the PER3 gene DNA methylation level. A cross-lag model was used to examine the bidirectional association between sleep quality and mental health. The PROCESS plug-in of SPSS software was used to analyse the moderating effects of PER3 gene DNA methylation. Results: Cross-lagged analyses suggested a significant bidirectional relationship between poor sleep quality and depressive symptoms, anxiety symptoms, and stress symptoms. Sleep quality at baseline was a significant predictor of depressive symptoms (β = 0.344, P < 0.001), anxiety symptoms (β = 0.348, P < 0.001), and stress symptoms (β = 0.324, P < 0.001) half a year later. Depressive symptoms (β = 0.049, P < 0.001), anxiety symptoms (β = 0.055, P < 0.001), and stress symptoms (β = 0.063, P < 0.001) at baseline were also significant predictors of poor sleep quality half a year later. Furthermore, PER3 gene DNA methylation has negative moderating effects between sleep quality at baseline and depressive symptoms (β = -11.706, P = 0.012), anxiety symptoms (β = -10.289, P = 0.019), and stress symptoms (β = -10.799, P = 0.024) half a year later and a sex difference. Among boys, PER3 gene DNA methylation has positive moderating effects between anxiety symptoms at baseline and sleep quality (β = 3.337, P = 0.018) half a year later. However, there was no association between mental health at baseline and sleep quality half a year later among girls. Conclusion: Bidirectional relationships were identified between sleep quality and mental health among Chinese young adults during the study period. DNA methylation evidence supports a negative moderating effect of PER3 gene DNA methylation on the relationship between sleep quality at baseline and mental health half a year later and had sex differences. Among boys, PER3 gene DNA methylation had positive moderating effects between anxiety symptoms at baseline and sleep quality half a year later. These findings point to the importance of circadian clock gene DNA methylation in the relationship between sleep quality and mental health.
Article
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Individual preferred timing of sleep and activity patterns, known as circadian preference, ranges from definitely morning types to definitely evening types. Being an evening type has been linked to adverse sleep and mental health outcomes. This study aimed to explore the associations between circadian preference and self-reported sleep, depression, anxiety, quality of life, loneliness, and self-harm/suicidal thoughts. Data stem from a national survey of students in higher education in Norway (the SHoT-study). All 169,572 students in Norway were invited to participate, and 59,554 students (66.5% women) accepted (response rate = 35.1%). Circadian preference was associated with sleep and mental health outcomes in a dose-response manner. For both genders, being an evening type (either definitely evening or more evening than morning) was associated with an increase in age-adjusted relative risk (RR-adjusted; range = 1.44 to 2.52 vs. 1.15 to 1.90, respectively) across all outcomes compared with definitely morning types. Overall, the present study provides further evidence that evening circadian preference is associated with adverse sleep and mental health outcomes in young adults. As such, future efforts to improve sleep and mental health in young adults should consider their circadian preferences.
Article
The daily alternation between sleep and wakefulness is one of the most dominant features of our lives and is a manifestation of the intrinsic 24 h rhythmicity underlying almost every aspect of our physiology. Circadian rhythms are generated by networks of molecular oscillators in the brain and peripheral tissues that interact with environmental and behavioural cycles to promote the occurrence of sleep during the environmental night. This alignment is often disturbed, however, by contemporary changes to our living environments, work or social schedules, patterns of light exposure, and biological factors, with consequences not only for sleep timing but also for our physical and mental health. Characterised by undesirable or irregular timing of sleep and wakefulness, in this Series paper we critically examine the existing categories of circadian rhythm sleep–wake disorders and the role of the circadian system in their development. We emphasise how not all disruption to daily rhythms is driven solely by an underlying circadian disturbance, and take a broader, dimensional approach to explore how circadian rhythms and sleep homoeostasis interact with behavioural and environmental factors. Very few high-quality epidemiological and intervention studies exist, and wider recognition and treatment of sleep timing disorders are currently hindered by a scarcity of accessible and objective tools for quantifying sleep and circadian physiology and environmental variables. We therefore assess emerging wearable technology, transcriptomics, and mathematical modelling approaches that promise to accelerate the integration of our knowledge in sleep and circadian science into improved human health.
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Background Emerging research suggests that food intake timing, eating behavior and food preference are associated with aspects of the circadian system function but the role that the circadian system may play in binge eating (BE) behavior in humans remains unclear. Objective To systematically evaluate the evidence for circadian system involvement in BE behavior. Methods Systematic searches of PubMed, EMBASE, and Scopus were performed for reports published from inception until May 2020 (PROSPERO Registration CRD42020186325). Searches were conducted by combining Medical Subject Headings related to the circadian system, BE behavior, and/or interventions. Observational and interventional studies in humans with BE behavior published in peer-review journals in the English language were included. Studies were assessed using quality and risk of bias tools (AXIS, ROB 2.0, or ROBINS). Results The search produced 660 articles, 51 of which were included in this review. Of these articles, 46 were observational studies and 5 were interventional trials. Evidence from these studies suggests that individuals with BE behavior tend to have more food intake, more binge cravings, and more BE episodes later in the day. Hormonal and day/night locomotor activity rhythm disturbances may be associated with BE behavior. Furthermore, late diurnal preference (“eveningness”) was associated with BE behavior and chronobiological interventions that shift the circadian clock earlier (e.g., morning bright light therapy) were found to possibly decrease BE behavior. Substantive clinical overlap exists between BE and night eating behavior. However, there is a significant knowledge gap regarding their potential relationship with the circadian system. Limitations include the lack of studies that use best-established techniques to assess the chronobiology of BE behavior, heterogeneity of participants, diagnostic criteria, and study design, which preclude a meta-analytic approach. Conclusion Current evidence, although limited, suggests that the circadian system may play a role in the etiology of BE behavior. Further mechanistic studies are needed to fully characterize a potential role of the circadian system in BE behavior. A chronobiological approach to studying BE behavior may lead to identification of its neurobiological components and development of novel therapeutic interventions. Systematic review registration [ https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020186325 ], identifier [CRD42020186325].
Article
Background Accumulating evidence implicates sleep and circadian rhythm disturbance in obsessive-compulsive disorder (OCD). However, a multimethod characterization of sleep and circadian rhythms in OCD, their association with symptom severity, and the functional relationship between these variables is lacking. Methods The present study measured multiple indicators of sleep and circadian rhythms in a sample of adults with OCD, adults without OCD, and healthy controls (n = 74). Participants completed measures of morningness-eveningness, delayed sleep-wake phase disorder (DSWPD), insomnia symptoms, and OCD symptoms, as well as one week of sleep monitoring via a sleep diary and actigraphy. Results Delayed circadian rhythms (higher eveningness, later mid-sleep timing, and higher rates of DSWPD) and higher insomnia symptoms were observed in those with OCD compared to healthy controls, as well as associations between delayed circadian rhythms and insomnia symptoms and OCD symptom severity across the full sample. Further, insomnia symptoms mediated the relationship between delayed circadian rhythms and OCD symptoms. In contrast, there were no links between total sleep time or sleep quality and OCD. Limitations Data collection during COVID-19 pandemic, correlational data, no physiological measure of circadian rhythms. Conclusions These findings highlight a robust association between delayed circadian rhythms and OCD and suggest insomnia symptoms may be one mechanism in this relationship. Sleep and circadian rhythm disturbance may be novel targets for OCD treatment.
Article
The aim of the present study was to adapt the Morningness-Eveningness-Stability Scale improved (MESSi) to the Spanish adolescent population, testing its factor structure and construct validity. The participants were 725 adolescents (52.9% girls; M = 14.8, SD = 1.99) who completed the MESSi, the Morningness Eveningness Scale of Children (MESC), questions about sleep habits adapted from the School Sleep Habits Survey, and self-reported academic performance. The psychometric results support a three-factor model with the factors of morning affect, eveningness, and distinctness, which show good internal consistency. The pattern of correlations between MESSi and the other measures was in the expected direction. The MESC correlated positively with morning affect and negatively with eveningness, whereas distinctness was uncorrelated. Boys reported higher morningness, whereas girls reported higher distinctness. Eveningness was negatively related to academic performance. Overall, the results support the validity and reliability of the Spanish adolescent version of the MESSi.
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The circadian rhythm is crucial for physiological and behavioral functions. Chronotype, which represents individual preferences for activity and performance, is associated with human health issues, particularly psychiatric disorders. This narrative review, which focuses on the relationship between chronotype and mental disorders, provides an insight into the potential mechanism. Recent evidence indicates that (1) the evening chronotype is a risk factor for depressive disorders and substance use disorders, whereas the morning chronotype is a protective factor. (2) Evening chronotype individuals with bipolar disorder tend to have more severe symptoms and comorbidities. (3) The evening chronotype is only related to anxiety symptoms. (4) The relationship between chronotype and schizophrenia remains unclear, despite increasing evidence on their link. (5) The evening chronotype is significantly associated with eating disorders, with the majority of studies have focused on binge eating disorders. Furthermore, the underlying mechanisms or influence factors are described in detail, including clock genes, brain characteristics, neuroendocrinology, the light/dark cycle, social factors, psychological factors, and sleep disorders. These findings provide the latest evidence on chronotypes and psychiatric disorders and serve as a valuable reference for researchers.
Article
Background The clinical importance of morningness-eveningness, especially in mood disorders, is prevailing. The differential relation of chronotype with diagnoses of early-onset mood disorders, mood symptoms, anxiety, and quality of life was evaluated. Methods Early-onset mood disorder patients [n = 419; 146 major depressive disorder (MDD); 123 bipolar I disorder (BDI); 150 bipolar II disorder (BDII)] from the Mood Disorder Cohort Research Consortium were assessed for chronotype using the composite scale for morningness (CSM) and its association with clinical variables obtained during the clinician-verified euthymic state. Results The mean total CSM of BDI was significantly higher than MDD and BDII (p < 0.001). In all types of mood disorders, higher total CSM was associated with lower Quick inventory of depressive symptomatology (p < 0.005) and higher WHO quality of life (p < 0.005). Such negative correlations between the total CSM and Montgomery-Asberg depression rating were significant in MDD and BDI (p < 0.05) and marginally significant in BDII (p = 0.077). CSM was a significant contributor to quality of life in BDI (p < 0.001) and BDII (p = 0.011), but it was not for MDD. Limitations The defined ‘euthymic state’ that may not fully reflect the remission of episode; limited generalizability due to clinical characteristic of early-onset mood disorder; the disparity between diurnal preference measured by the CSM and chronotype; possible effects of the last mood episode polarity and medication; and, lack of control group. Conclusion Less eveningness was associated with less severe depressive symptoms and better quality of life. This suggests that morningness may reduce residual depressive symptoms and recover function of patients.
Article
Рreference for later bedtimes and rise times characterize evening chronotypes. Evening chronotypes suffer from early work start times thereby contradicting their circadian rhythms, as a result, a late wake-up time on free days reflect an attempt to compensate for a sleep debt accumulated on work days. This leads to a misalignment in sleep timing between weekdays and weekends, known as social jetlag (SJL), which is associated with increased health risk. Here we analyze the risks that evening preferences related with SJL bear and their potential impact on health, and also talk about possible correction measures, primarily of a behavioral nature, using literature data from PubMed and Embase database. Evening chronotype can compromise the maintenance of a healthy lifestyle. Evening chronotypes are more prone to bedtime screen use, which can suppress melatonin rise and extend wakefulness activities far into the night, thus dragging sleep and meal timing to later periods. Preference towards later time-of-day is linked with higher intake of total calories and fats, as well as unhealthy dietary habits (breakfast skipping, snacking, longer eating duration). Evening chronotype also has been associated with high caffeinated drinks intake, alcohol consumption and smoking, low physical activities. It has been found that unhealthy behavior might function as the promoting factors to circadian misalignment and greater SJL. Interventions to prevent and control unhealthy behaviors among evening types should be included in preventive measures of SJL.
Article
Individual preference for morning or evening activities (chronotype), affect, hardiness, and talent are associated with a variety of performance outcomes. This longitudinal study was designed to investigate the degree to which these variables are associated with academic, physical, and military performance. Self-reported measures of chronotype, affect, and hardiness were collected from 1149 cadets from the Class of 2016 upon entry to the United States Military Academy. Talent, a composite of academic, leadership, and physical fitness scores were drawn from cadet records. Academic, military, and physical performance measures were collected at graduation 4 years later. The results indicated that a morning orientation was associated with better physical and military performance. Higher talent scores, as well as lower levels of negative affect, were associated with better performance across all three performance measures. Hardiness was only associated with military performance. The findings suggest that a morning orientation and less negative affect may result in better performance overall within a challenging and structured military environment. Future studies of chronotype shifts may provide further insight into associated performance benefits.
Article
Major depressive disorder (MDD) is frequently accompanied by sleep disturbance. Regarding diurnal preference (chronotype), sleep problems and low mood have been associated with evening orientation. Considering diurnal preference, we investigated subjective restorative value of sleep and actigraphy sleep parameters together with mood assessments twice a day, i.e. in the morning and evening, during weekdays and weekends in MDD psychiatric inpatients and healthy controls (HCs). The restorative value of sleep was higher during the weekend in HC, and bedtimes and risetimes were delayed during the weekend compared to weekdays in HC and MDD. Morning mood affected subjective sleep ratings in both groups, while association with symptom severity (BDI) in MDD remained insignificant. In HC, better evening mood was associated with later bedtimes. Regarding the chronotype in HC, evening orientation was associated with relatively low restorative value of sleep during weekdays, and morning orientation was associated with relatively higher actigraphy sleep efficiency during weekdays compared to weekend. In MDD, an association of evening orientation with later rise times could be observed, while no chronotype dependent effect emerged regarding the restorative value of sleep or sleep efficiency. Our results emphasize that research on sleep in MDD should incorporate weekdays as well as weekends, chronotype assessment, and measures of morning and evening mood, as these can be associated with ratings of the subjective restorative value of sleep (i.e. in our study, better morning mood was associated with higher restorative values), but also with behavioral sleep parameters (i.e. in our study, more positive evening mood was associated with later bedtimes). Potentially, the restorative value of sleep in MDD evening types can be improved by maintaining a regular sleep schedule, which needs to be investigated in an experimental design.
Article
Major depressive disorder (MDD) is frequently accompanied by sleep disturbance. Regarding diurnal preference (chronotype), sleep problems and low mood have been associated with evening orientation. Considering diurnal preference, we investigated subjective restorative value of sleep and actigraphy sleep parameters together with mood assessments twice a day, i.e. in the morning and evening, during weekdays and weekends in MDD psychiatric inpatients and healthy controls (HCs). The restorative value of sleep was higher during the weekend in HC, and bedtimes and risetimes were delayed during the weekend compared to weekdays in HC and MDD. Morning mood affected subjective sleep ratings in both groups, while association with symptom severity (BDI) in MDD remained insignificant. In HC, better evening mood was associated with later bedtimes. Regarding the chronotype in HC, evening orientation was associated with relatively low restorative value of sleep during weekdays, and morning orientation was associated with relatively higher actigraphy sleep efficiency during weekdays compared to weekend. In MDD, an association of evening orientation with later rise times could be observed, while no chronotype dependent effect emerged regarding the restorative value of sleep or sleep efficiency. Our results emphasize that research on sleep in MDD should incorporate weekdays as well as weekends, chronotype assessment, and measures of morning and evening mood, as these can be associated with ratings of the subjective restorative value of sleep (i.e. in our study, better morning mood was associated with higher restorative values), but also with behavioral sleep parameters (i.e. in our study, more positive evening mood was associated with later bedtimes). Potentially, the restorative value of sleep in MDD evening types can be improved by maintaining a regular sleep schedule, which needs to be investigated in an experimental design.
Article
Chronotype is related to mental health, with evening chronotypes being more susceptible to psychological disorders than intermediate and morning types. The present study investigated the relationship between chronotype, mental health, sleep quality, and social support in Canadian young adults. We surveyed 3160 university students aged 18–35 years. Participants completed the Morningness–Eveningness Questionnaire, the Hospital Anxiety and Depression Scale, the Mindful Attention Awareness Scale, the Pittsburgh Sleep Quality Index, and the Medical Outcomes Study – Social Support Survey. We conducted Bonferroni‐corrected one‐way analyses of covariance with post hoc paired comparisons to determine the relationship between the aforementioned variables, with age and sex as covariates. We further looked at the moderation of social support on the relationship between chronotype and sleep quality. Overall, 55%, 36% and 9% of participants were classified as intermediate, evening and morning types, respectively. There was a significant difference between chronotype on levels of depression, anxiety, and sleep quality, with evening types reporting more severe symptomology than morning‐types and intermediate types. Morning types reported greater levels of overall social support and mindfulness. Evening types reported the lowest levels of all types of social support. Social support did not moderate the relationship between chronotype and sleep quality. This study further demonstrates the association between worse psychological well‐being and eveningness and between more social support, and mindfulness in morning chronotype young adults. Education and intervention are warranted to help evening chronotypes manage the potential negative features of their circadian rhythm, as well as to cultivate a greater sense of social support and mindfulness.
Article
Importance Morning diurnal preference is associated with reduced risk of major depressive disorder (MDD); however, causality in this association is uncertain. Objective To examine the association of genetically proxied morning diurnal preference with depression risk using mendelian randomization. Design, Setting, and Participants This 2-sample mendelian randomization study used summary-level genetic associations with diurnal preference and MDD. Up to 340 genetic loci associated with diurnal preference in a meta-analysis of the UK Biobank and 23andMe cohorts were considered as genetic proxies for diurnal preference. The effect size of these variants was scaled using genetic associations with accelerometer-based measurement of sleep midpoint. Genetic associations with MDD were obtained from a meta-analysis of genome-wide association studies data from the Psychiatric Genomics Consortium and UK Biobank. The inverse-variance weighted method was used to estimate the association of genetically proxied morning diurnal preference, corresponding to a 1-hour earlier sleep midpoint, with MDD risk. Exposures Morning diurnal preference scaled to a 1-hour earlier, objectively measured sleep midpoint. Main Outcomes and Measures Risk of MDD, including self-reported and clinically diagnosed cases, as ascertained in meta-analyses of genome-wide association studies. Results A total of 697 828 individuals (all of European ancestry) were in the UK Biobank and 23andMe cohorts; 85 502 in the UK Biobank had measurements of the sleep midpoint. A further 170 756 individuals with MDD and 329 443 control participants (all of European ancestry) were in the Psychiatric Genomics Consortium and UK Biobank data. Genetically proxied earlier diurnal preference was associated with a 23% lower risk of depression (odds ratio [OR] per 1-hour earlier sleep midpoint, 0.77 [95% CI, 0.63-0.94]; P = .01). This association was similar when restricting analysis to individuals with MDD as stringently defined by the Psychiatric Genomics Consortium (OR, 0.73 [95% CI, 0.54-1.00]; P = .05) but not statistically significant when defined by hospital-based billing codes in the UK Biobank (OR, 0.64 [95% CI, 0.39-1.06]; P = .08). Sensitivity analyses examining potential bias due to pleiotropy or reverse causality showed similar findings (eg, intercept [SE], 0.00 [0.001]; P = .66 by Egger intercept test). Conclusions and Relevance The results of this mendelian randomization study support a protective association of earlier diurnal preference with risk of MDD and provide estimates contextualized to an objective sleep timing measure. Further investigation in the form of randomized clinical trials may be warranted.
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Objectives This is the first general population study to evaluate whether evening chronotypes (E) have poorer work ability (WA) and higher probability for early disability pensions (DPs) than morning types (M) in middle age. Methods Among non-retired individuals (n=5831; 2672 men, 3159 women) of the Northern Finland Birth Cohort 1966, chronotype was determined at the age of 46 years with shortened Morningness–Eveningness Questionnaires in 2012. The outcomes were poor WA in 2012, indicated by scores 0–7/10 of Work Ability Score, and registered emergence of DPs in 2013–2016. Multivariate logistic and Cox regression analyses were separately adjusted for factors related to sleep, health and behaviours, sociodemographic and economic factors, or working times. Results E-types represented 10% (n=264) of men and 12% (n=382) of women. Compared with M-types, the unadjusted ORs with 95% CIs of poor WA for E-type men and women were 2.24 (95% CI 1.62 to 3.08) and 2.33 (95% CI 1.74 to 3.10), respectively. The odds remained statistically significant and approximately twofold in all separate adjustment models tested. During 2013–2016, 8 (3.0%) E-type men and 10 (2.6%) E-type women were granted DP, which, compared with M-types, represented a higher HR that was statistically significant for men (HR 3.12, 95% CI 1.27 to 7.63) and remained significant except when multiple sleep variables or working times were adjusted for. Conclusions Eveningness appears a previously unrecognised risk factor for poor WA and early disability. We suggest that individual chronotype be considered in attempts to lengthen work careers.
Article
Both evening chronotype and shift work are associated with depressive symptoms. This study examined whether the association between shift work and mood disorders and sleep problems varies by chronotype. The study population included 10637 participants from the Finnish Hospital Personnel Cohort Study. Work schedule was assessed using repeated questionnaires between 2000 and 2017. Chronotype, assessed using a single item from the Diurnal Type Scale, was categorized into definite morning, somewhat morning, somewhat evening, and definite evening types. The presence of mood disorders was identified by the 12-item General Health Questionnaire. Sleep problems were assessed by self-reported frequency of difficulty falling asleep and maintaining asleep. Longitudinal fixed effects models were used to examine the associations between shift work and the presence of mood disorders and sleep problems, stratified by chronotype. We found that fixed night work was associated with mood disorders among somewhat evening (adjusted odds ratio [OR] 1.91, 95% CI 1.09-3.34) and definite evening-type workers (adjusted OR 2.05, 95% CI 1.06-3.98). Shift work with night shifts was associated with mood disorders among definite evening-type workers (adjusted OR 1.75, 95% CI 1.18-2.60). Similarly, fixed night work was associated with difficulty maintaining sleep only among evening-type workers. In conclusion, evening chronotype increase the vulnerability to mood disorders and sleep disturbances related to night work.
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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.
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Background Whether you are a morning lark or a night owl has proven to be a key contributor in the timing of peak athletic performance. Recent evidence suggests that accounting for these differences, known as one’s chronotype, results in significantly different diurnal performance profiles. However, there is limited research investigating multiple measures of performance simultaneously over the course of a socially constrained day. Objectives This study aimed to investigate the impact of chronotype on indices of cognitive and physical performance at different times of day in healthy volunteers. Methods We recruited 56 healthy individuals categorised as early (ECT, n = 25) or late (LCT, n = 31) chronotypes using the Munich ChronoType Questionnaire, circadian phase markers and objective actigraphy. Measures of cognitive and physical performance, along with self-reported daytime sleepiness, were taken at multiple times of day (14:00 h, 20:00 h and 08:00 h the following morning). Results Here, we find significantly different diurnal variation profiles between ECTs and LCTs, for daytime sleepiness, psychomotor vigilance, executive function and isometric grip strength. LCTs were significantly impaired in all measures in the morning compared to ECTs. Conclusion Our results provide evidence to support the notion that ‘night owls’ are compromised earlier in the day. We offer new insight into how differences in habitual sleep patterns and circadian rhythms impact cognitive and physical measures of performance. These findings may have implications for the sports world, e.g. athletes, coaches and teams, who are constantly looking for ways to minimise performance deficits and maximise performance gains.
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Later chronotype (i.e. evening preference) and later timing of sleep have been associated with greater morbidity, including higher rates of metabolic dysfunction and cardiovascular disease (CVD). However, no one has examined whether chronotype is associated with mortality risk to date. Our objective was to test the hypothesis that being an evening type is associated with increased mortality in a large cohort study, the UK Biobank. Our analysis included 433 268 adults aged 38–73 at the time of enrolment and an average 6.5-year follow-up. The primary exposure was chronotype, as assessed through a single self-reported question-defining participants as definite morning types, moderate morning types, moderate evening types or definite evening types. The primary outcomes were all-cause mortality and mortality due to CVD. Prevalent disease was also compared among the chronotype groups. Analyses were adjusted for age, sex, ethnicity, smoking, body mass index, sleep duration, socioeconomic status and comorbidities. Greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of all comorbidities. Comparing definite evening type to definite morning type, the associations were strongest for psychological disorders (OR 1.94, 95% CI 1.86–2.02, p = < 0.001), followed by diabetes (OR 1.30, 95% CI 1.24–1.36, p = < 0.001), neurological disorders (OR 1.25, 95% CI 1.20–1.30, p = < 0.001), gastrointestinal/abdominal disorders (OR 1.23, 95% CI 1.19–1.27, p = < 0.001) and respiratory disorders (OR 1.22, 95% CI 1.18–1.26, p = < 0.001). The total number of deaths was 10 534, out of which 2127 were due to CVD. Greater eveningness, based on chronotype as an ordinal variable, was associated with a small increased risk of all-cause mortality (HR 1.02, 95% CI 1.004–1.05, p = 0.017) and CVD mortality (HR 1.04, 95% CI 1.00–1.09, p = 0.06). Compared to definite morning types, definite evening types had significantly increased risk of all-cause mortality (HR 1.10, 95% CI 1.02–1.18, p = 0.012). This first report of increased mortality in evening types is consistent with previous reports of increased levels of cardiometabolic risk factors in this group. Mortality risk in evening types may be due to behavioural, psychological and physiological risk factors, many of which may be attributable to chronic misalignment between internal physiological timing and externally imposed timing of work and social activities. These findings suggest the need for researching possible interventions aimed at either modifying circadian rhythms in individuals or at allowing evening types greater working hour flexibility.
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Study Objectives To investigate the short- and longer-term impact of a 45-min delay in school start time on sleep and well-being of adolescents. Methods The sample consisted of 375 students in grades 7–10 (mean age ± SD: 14.6 ± 1.15 years) from an all-girls’ secondary school in Singapore that delayed its start time from 07:30 to 08:15. Self-reports of sleep timing, sleepiness, and well-being (depressive symptoms and mood) were obtained at baseline prior to the delay, and at approximately 1 and 9 months after the delay. Total sleep time (TST) was evaluated via actigraphy. Results After 1 month, bedtimes on school nights were delayed by 9.0 min, while rise times were delayed by 31.6 min, resulting in an increase in time in bed (TIB) of 23.2 min. After 9 months, the increase in TIB was sustained, and TST increased by 10.0 min relative to baseline. Participants also reported lower levels of subjective sleepiness and improvement in well-being at both follow-ups. Notably, greater increase in sleep duration on school nights was associated with greater improvement in alertness and well-being. Conclusions Delaying school start time can result in sustained benefits on sleep duration, daytime alertness, and mental well-being even within a culture where trading sleep for academic success is widespread.
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Circadian rhythms, metabolism, and nutrition are intimately linked [1, 2], although effects of meal timing on the human circadian system are poorly understood. We investigated the effect of a 5-hr delay in meals on markers of the human master clock and multiple peripheral circadian rhythms. Ten healthy young men undertook a 13-day laboratory protocol. Three meals (breakfast, lunch, dinner) were given at 5-hr intervals, beginning either 0.5 (early) or 5.5 (late) hr after wake. Participants were acclimated to early meals and then switched to late meals for 6 days. After each meal schedule, participants’ circadian rhythms were measured in a 37-hr constant routine that removes sleep and environmental rhythms while replacing meals with hourly isocaloric snacks. Meal timing did not alter actigraphic sleep parameters before circadian rhythm measurement. In constant routines, meal timing did not affect rhythms of subjective hunger and sleepiness, master clock markers (plasma melatonin and cortisol), plasma triglycerides, or clock gene expression in whole blood. Following late meals, however, plasma glucose rhythms were delayed by 5.69 ± 1.29 hr (p < 0.001), and average glucose concentration decreased by 0.27 ± 0.05 mM (p < 0.001). In adipose tissue, PER2 mRNA rhythms were delayed by 0.97 ± 0.29 hr (p < 0.01), indicating that human molecular clocks may be regulated by feeding time and could underpin plasma glucose changes. Timed meals therefore play a role in synchronizing peripheral circadian rhythms in humans and may have particular relevance for patients with circadian rhythm disorders, shift workers, and transmeridian travelers.
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The 10-min psychomotor vigilance task (PVT) has often been used to assess the impact of sleep loss on performance. Due to time constraints, however, regular testing may not be practical in field studies. The aim of the present study was to examine the suitability of tests shorter than 10 min. in duration. Changes in performance across a night of sustained wakefulness were compared during a standard 10-min PVT, the first 5 min of the PVT, and the first 2 min of the PVT. Four performance metrics were assessed: (1) mean reaction time (RT), (2) fastest 10% of RT, (3) lapse percentage, and (4) slowest 10% of RT. Performance during the 10-min PVT significantly deteriorated with increasing wakefulness for all metrics. Performance during the first 5 min and the first 2 min of the PVT deteriorated in a manner similar to that observed for the whole 10-min task, with all metrics except lapse percentage displaying significant impairment across the night. However, the shorter the task sampling time, the less sensitive the test is to sleepiness. Nevertheless, the 5-min PVT may provide a viable alternative to the 10-min PVT for some performance metrics.
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Team performance is a complex phenomenon involving numerous influencing factors including physiology, psychology, and management. Biological rhythms and the impact of circadian phenotype have not been studied for their contribution to this array of factors so far despite our knowledge of the circadian regulation of key physiological processes involved in physical and mental performance. This study involved 216 individuals from 12 different teams who were categorized into circadian phenotypes using the novel RBUB chronometric test. The composition of circadian phenotypes within each team was used to model predicted daily team performance profiles based on physical performance tests. Our results show that the composition of circadian phenotypes within teams is variable and unpredictable. Predicted physical peak performance ranged from 1:52 to 8:59 p.m. with performance levels fluctuating by up to 14.88% over the course of the day. The major predictor for peak performance time in the course of a day in a team is the occurrence of late circadian phenotypes. We conclude that circadian phenotype is a performance indicator in teams that allows new insight and a better understanding of team performance variation in the course of a day as often observed in different groupings of individuals.
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Today's modern society is exposed to artificial electric lighting in addition to the natural light-dark cycle. Studies assessing the impact of electric light exposure on sleep and its relation to work hours are rare due to the ubiquitous presence of electricity. Here we report a unique study conducted in two phases in a homogenous group of rubber tappers living and working in a remote area of the Amazon forest, comparing those living without electric light (n = 243 in first phase; n = 25 in second phase) to those with electric light at home (n = 97 in first phase; n = 17 in second phase). Questionnaire data (Phase 1) revealed that rubber tappers with availability of electric light had significantly shorter sleep on work days (30 min/day less) than those without electric light. Analysis of the data from the Phase 2 sample showed a significant delay in the timing of melatonin onset in workers with electric light compared to those without electric light (p < 0.01). Electric lighting delayed sleep onset and reduced sleep duration during the work week and appears to interfere with alignment of the circadian timing system to the natural light/dark cycle.
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The aim of this study was to compare morning and evening time-trial performance, RPE and mood state of trained swimmers, taking into account chronotype, habitual training time-of-day and PERIOD3 (PER3) variable number tandem repeat genotype. Twenty-six swimmers (18 males, age: 32.6 ± 5.7 years) swam 200 m time trials (TT) at 06h30 and 18h30 in a randomised order. There was no difference between morning and evening performance when the swimmers were considered as a single group (06h30: 158.8 ± 22.7 s, 18h30: 158.5 ± 22.0 s, p = 0.611). However, grouping swimmers by chronotype and habitual training time-of-day allowed us to detect significant diurnal variation in performance, such that morning-type swimmers and those who habitually train in the morning were faster in the 06h30 TT (p = 0.036 and p = 0.011, respectively). This was accompanied by lower ratings of perceived exertion (RPE) scores post-warm-up, higher vigour and lower fatigues scores prior to the 06h30 TT in morning-type swimmers or those who trained in the morning. Similarly, neither types and those who trained in the evenings had lower fatigue and higher vigour prior to the 18h30 TT. It appears that both chronotype and habitual training time-of-day need to be considered when assessing diurnal variation in performance. From a practical point of view, athletes and coaches should be aware of the potentially powerful effect of training time on shifting time-of-day variation in performance.
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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.
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Travel across time zones causes jet lag and is accompanied by deleterious effects on sleep and performance in athletes. These poor performances have been evaluated in field studies but not in laboratory conditions. The purpose of this study was to evaluate, in athletes, the impact of 5-h phase advance on the architecture of sleep and physical performances (Wingate test). In a sleep laboratory, 16 male athletes (age: 22.2 ± 1.7 years, height: 178.3 ± 5.6 cm, body mass: 73.6 ± 7.9 kg) spent 1 night in baseline condition and 2 nights, 1 week apart, in phase shift condition recorded by electroencephalography to calculate sleep architecture variables. For these last 2 nights, the clock was advanced by 5 h. Core body temperature rhythm was assessed continuously. The first night with phase advance decreased total sleep time, sleep efficiency, sleep onset latency, stage 2 of nonrapid eye movement (N2), and rapid eye movement (REM) sleep compared with baseline condition, whereas the second night decreased N2 and increased slow-wave sleep and REM, thus improving the quality of sleep. After phase advance, mean power improved, which resulted in higher lactatemia. Acrophase and bathyphase of temperature occurred earlier and amplitude decreased in phase advance but the period was not modified. These results suggest that a simulated phase shift contributed to the changes in sleep architecture, but did not significantly impair physical performances in relation with early phase adjustment of temperature to the new local time.
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Clinical practice related to sleep problems and sleep disorders has been expanding rapidly in the last few years, but scientific research is not keeping pace. Sleep apnea, insomnia, and restless legs syndrome are three examples of very common disorders for which we have little biological information. This new book cuts across a variety of medical disciplines such as neurology, pulmonology, pediatrics, internal medicine, psychiatry, psychology, otolaryngology, and nursing, as well as other medical practices with an interest in the management of sleep pathology. This area of research is not limited to very young and old patients-sleep disorders reach across all ages and ethnicities. Sleep Disorders and Sleep Deprivation presents a structured analysis that explores the following: Improving awareness among the general public and health care professionals. Increasing investment in interdisciplinary somnology and sleep medicine research training and mentoring activities. Validating and developing new and existing technologies for diagnosis and treatment. This book will be of interest to those looking to learn more about the enormous public health burden of sleep disorders and sleep deprivation and the strikingly limited capacity of the health care enterprise to identify and treat the majority of individuals suffering from sleep problems. © 2006 by the National Academy of Sciences. All rights reserved.