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© 2023 The Authors. Journal of Pineal Research published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made., Due to time zones, sun time and local time rarely match. The difference between local and sun time, which we designate by Solar Jet Lag (SoJL), depends on location within a time zone and can range from zero to several hours. Daylight saving time (DST) simply adds 1 h to SoJL, independently of the location. We hypothesised that the impact of DST is particularly problematic in patients with delayed sleep-wake phase disorder (DSWPD), worsening their sleep debt. DSWPD is characterised by a chronic misalignment between the internal and social timing, reflected by an inability to fall asleep and wake-up at conventional or socially acceptable times. We analysed the clinical records of 162 DSWPD patients from a sleep medicine centre in Lisbon, Portugal (GMTzone), and separated them into two groups: the ones diagnosed across DST or across Standard Time (ST). We included 82 patients (54.9% male; age: median [Q1 , Q3 ] 34.5 [25.0, 45.3]; range 16-92; 54 in DST and 28 in ST) who had Dim Light Melatonin Onset (DLMO) measured as a marker for the circadian phase and sleep timing (onset, SO, mid-point, MS and end, SE) self-reported separately for work- and work-free days. Differences between ST and DST were compared using Mann-Whitney or Student's t-tests. On a weekly average, patients in DST slept less (difference between medians of 37 min. p < .01), mainly due to sleep on workdays (SDw, p < .01), which also correlated with SoJL (rsp = .38, p < .01). While the time from DLMO to SO was similar in those in ST or those in DST, the time from DLMO to SE was significantly shorter for those in DST. The average duration between DLMO and sleep end was close to 10.5 h in ST, the biological night length described in the literature. Our results favour perennial ST and suggest assigning time-zones close to sun time to prevent social jetlag and sleep deprivation.

Seit mehr als 60 Jahren wird die Aktigraphie eingesetzt, um den Schlaf-Wach-Rhythmus objektiv zu erfassen. Zunehmend werden verbesserte moderne Gerate angewendet, um schlafmedizinische Erkrankungen im klinischen Rahmen zu diagnostizieren. Aktigraphen sind zwar weniger genau als die Polysomnographie, aber ihr groster Vorteil liegt in der kostengunstigen Sammlung objektiver Daten uber langere Zeitraume unter Alltagsbedingungen. Da die Kosten der Handgelenksaktigraphie derzeit nicht erstattet werden, hat dieses Verfahren bisher keine breite Akzeptanz erlangt. In der vorliegenden Arbeit wird ein Uberblick uber die wesentlichen klinischen Anwendungen der Aktigraphie sowie uber die Empfehlungen der Fachgesellschaften gegeben.

Polyphasic sleep is the practice of distributing multiple short sleep episodes across the 24-hour day rather than having one major and possibly a minor ("nap") sleep episode each day. While the prevalence of polyphasic sleep is unknown, anecdotal reports suggest attempts to follow this practice are common, particularly among young adults. Polyphasic-sleep advocates claim to thrive on as little as 2 hours of total sleep per day. However, significant concerns have been raised that polyphasic sleep schedules can result in health and safety consequences. We reviewed the literature to identify the impact of polyphasic sleep schedules (excluding nap or siesta schedules) on health, safety, and performance outcomes. Of 40,672 potentially relevant publications, with 2,023 selected for full-text review, 22 relevant papers were retained. We found no evidence supporting benefits from following polyphasic sleep schedules. Based on the current evidence, the consensus opinion is that polyphasic sleep schedules, and the sleep deficiency inherent in those schedules, are associated with a variety of adverse physical health, mental health, and performance outcomes. Striving to adopt a schedule that significantly reduces the amount of sleep per 24 hours and/or fragments sleep into multiple episodes throughout the 24-hour day is not recommended.

Light at night (LAN) has been associated with negative health consequences and metabolic risk factors. Little is known about the prevalence of LAN in older adults in the United States and its association with CVD risk factors. We tested the hypothesis that LAN in older age is associated with higher prevalence of individual CVD risk factors. Five hundred and fifty-two community-dwelling adults aged 63−84 years underwent an examination of CVD risk factor profiles and 7-day actigraphy recording for activity and light measures. Associations between actigraphy-measured LAN, defined as no light vs. light within the 5-hour nadir (L5), and CVD risk factors, including obesity, diabetes, hypertension, and hypercholesterolemia, were examined, after adjusting for age, sex, race, season of recording, and sleep variables. LAN exposure was associated with a higher prevalence of obesity (multivariable-adjusted odds ratio [OR] 1.82 [95% CI 1.26−2.65]), diabetes (OR 2.00 [1.19−3.43]), and hypertension (OR 1.74 [1.21−2.52]) but not with hypercholesterolemia. LAN was also associated with (1) later timing of lowest light exposure (L5-light) and lowest activity (L5-activity), (2) lower inter-daily stability and amplitude of light exposure and activity, and (3) higher wake after sleep onset. Habitual LAN in older age is associated with concurrent obesity, diabetes, and hypertension. Further research is needed to understand long-term effects of LAN on cardiometabolic risks.

Actigraphy has been used for more than 60 years to objectively measure sleep–wake rhythms. Improved modern devices are increasingly employed to diagnose sleep medicine disorders in the clinical setting. Although less accurate than polysomnography, the chief advantage of actigraphs lies in the cost-effective collection of objective data over prolonged periods of time under everyday conditions. Since the cost of wrist actigraphy is not currently reimbursed, this method has not enjoyed wide acceptance to date. The present article provides an overview of the main clinical applications of actigraphy, including the recommendations of specialist societies.

The study aimed to explore chronotype-specific effects of two versus four consecutive morning or night shifts on sleep-wake behavior. Sleep debt and social jetlag (a behavioral proxy of circadian misalignment) were estimated from sleep diary data collected for 5 weeks in a within-subject field study of 30 rotating night shift workers (29.9 ± 7.3 years, 60% female). Mixed models were used to examine whether effects of shift sequence length on sleep are dependent on chronotype, testing the interaction between sequence length (two vs. four) and chronotype (determined from sleep diaries). Analyses of two versus four morning shifts showed no significant interaction effects with chronotype. In contrast, increasing the number of night shifts from two to four increased sleep debt in early chronotypes, but decreased sleep debt in late types, with no change in intermediate ones. In early types, the higher sleep debt was due to accumulated sleep loss over four night shifts. In late types, sleep duration did not increase over the course of four night shifts, so that adaptation is unlikely to explain the observed lower sleep debt. Late types instead had increased sleep debt after two night shifts, which was carried over from two preceding morning shifts in this schedule. Including naps did not change the findings. Social jetlag was unaffected by the number of consecutive night shifts. Our results suggest that consecutive night shifts should be limited in early types. For other chronotypes, working four night shifts might be a beneficial alternative to working two morning and two night shifts. Studies should record shift sequences in rotating schedules.

© 2021 The Authors. Journal of Sleep Research published by John Wiley & Sons Ltd on behalf of European Sleep Research Society., Light is an important regulator of daily human physiology in providing time-of-day information for the circadian clock to stay synchronised with the 24-hr day. The coronavirus disease 2019 (COVID-19) pandemic led to social restrictions in many countries to prevent virus spreading, restrictions that dramatically altered daily routines and limited outdoor daylight exposure. We previously reported that sleep duration increased, social jetlag decreased, and mid-sleep times delayed during social restrictions (Global Chrono Corona Survey, N = 7,517). In the present study, we investigated in the same dataset changes in wellbeing and their link to outdoor daylight exposure, and sleep-wake behaviour. In social restrictions, median values of sleep quality, quality of life, physical activity and productivity deteriorated, while screen time increased, and outdoor daylight exposure was reduced by ~58%. Yet, many survey participants also reported no changes or even improvements. Larger reductions in outdoor daylight exposure were linked to deteriorations in wellbeing and delayed mid-sleep times. Notably, sleep duration was not associated with outdoor daylight exposure loss. Longer sleep and decreased alarm-clock use dose-dependently correlated with changes in sleep quality and quality of life. Regression analysis for each wellbeing aspect showed that a model with six predictors including both levels and their deltas of outdoor daylight exposure, sleep duration and mid-sleep timing explained 5%-10% of the variance in changes of wellbeing scores (except for productivity). As exposure to daylight may extenuate the negative effects of social restriction and prevent sleep disruption, public strategies during pandemics should actively foster spending more daytime outdoors.

© 2020 Elsevier B.V. All rights reserved., Objectives: We aimed to compare three variants of the Pittsburgh Sleep Quality Index (PSQI usual, work- and work-free days: PSQIu, PSQIw, PSQIf) and to assess whether chronotype (MSFsc)/social jetlag (SJL) are associated with sleep quality in patients with sleep disorders (SD). Methods: In sum, 431 SD patients and 338 subjects from the general population (GP) were included. Participants filled in three variants of the PSQI and the Munich ChronoType Questionnaire (MCTQ). We used Generalized Estimating Equations (GEE) to investigate effects of group (GP, SD), PSQI (usual, work or free) and their interaction (group∗PSQI) on scores. To investigate associations between MSFsc/SJL and the difference between PSQIw and PSQIf (PSQIdiff) in patients with SD we used linear regressions (N = 352). We used Sobel to test whether there was a mediation effect of SJL on the association between MSFsc and PSQIdiff. Results: PSQI scores differed between groups (p < 0.001). Post-hoc analysis revealed a significant difference between PSQIu vs. PSQIf and PSQIw vs. PSQIf with PSQIf presenting lower scores, while PSQIu vs. PSQIw did not differ in any group. In line with previous findings, SJL was associated to PSQIdiff in SD patients. Conclusions: PSQIu mainly represents sleep quality on workdays also in SD patients. Being a late chronotype seems to be associated with higher differences in sleep quality on work-vs. free days mostly when it coincides with societal time constraints. Since sleep quality is poorer on workdays even in SD patients, we suggest that treatment strategies should address social aspects affecting sleep, including ways of minimizing SJL., This study was financed in part by the Fundação para a Ciência e Tecnologia (FCT) PhD research grant PDE/BDE/114584/2016, the Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES - PVE A046/2013) - Finance Code 001, and the Deutscher Akademischer Austauschdienst (CAPES/DAAD - PROBRAL 12/2017).

Irregular light–dark cycles and circadian/sleep disturbances have been suggested as risk or co-occurring factors in depression. Among a set of metrics developed to quantify strain on the circadian system, social jetlag (SJL) has been put forward as a measure of the discrepancy between biological and social clocks. Here, we approached the question on whether light exposure and SJL would also be associated with depressive symptoms in Quilombola communities in Southern Brazil. These rural communities are void of potential confounders of modern lifestyles and show low levels of SJL. 210 Quilombolas (age range 16–92; 56% women) were asked about their sleep times and light exposure using the Munich ChronoType Questionnaire (MCTQ). The Beck Depression Inventory (BDI) was used to assess depressive symptoms. Additionally, we analyzed 7-day actimetry recordings in 124 subjects. BDI scores higher than 10 (having clinically significant depressive symptoms; controlled for age and sex in the multivariate analysis) were positively associated with SJL >1 h and negatively associated with median light exposure during the day, especially in the morning from 8:00 to 10:00. Our results suggest that low light exposure during the day, and higher levels of SJL are associated with depressive symptoms; longitudinal and experimental studies are needed to understand the underlying mechanisms. Nevertheless, we highlight the potential of treatment strategies aimed at decreasing circadian strain and insufficient light exposure, which are suggested as areas of further research in Psychiatry.

The increasing availability and complexity of sleep and circadian data are equally exciting and challenging. The field is in constant technological development, generating better high-resolution physiological and molecular data than ever before. Yet, the promise of large-scale studies leveraging millions of patients is limited by suboptimal approaches for data sharing and interoperability. As a result, integration of valuable clinical and basic resources is problematic, preventing knowledge discovery and rapid translation of findings into clinical care. To understand the current data landscape in the sleep and circadian domains, the Sleep Research Society (SRS) and the Sleep Research Network (now a task force of the SRS) organized a workshop on informatics and data harmonization, presented at the World Sleep Congress 2019, in Vancouver, Canada. Experts in translational informatics gathered with sleep research experts to discuss opportunities and challenges in defining strategies for data harmonization. The goal of this workshop was to fuel discussion and foster innovative approaches for data integration and development of informatics infrastructure supporting multi-site collaboration. Key recommendations included collecting and storing findable, accessible, interoperable, and reusable data; identifying existing international cohorts and resources supporting research in sleep and circadian biology; and defining the most relevant sleep data elements and associated metadata that could be supported by early integration initiatives. This report introduces foundational concepts with the goal of facilitating engagement between the sleep/circadian and informatics communities and is a call to action for the implementation and adoption of data harmonization strategies in this domain.

Chronobiology is a thriving research field that spans all biomedical disciplines ranging from molecular biology and metabolism to psychology and internal medicine. Circadian rhythms are generated at the molecular level in practically all cells of the body. This ensemble of clocks forms the “circadian system” that coordinates every aspect of our biology on a daily basis—from the cells, tissues and organs up to the concerted regulation of metabolism or higher functions like sleep–wake behaviour, immune responses or cognition. With the help of a “master clock” in the brain, the mammalian circadian system actively synchronises (entrains) to light and darkness via the eyes. Industrialisation and urbanisation have drastically changed the way we expose ourselves to light and darkness and consequently how our clocks entrain. These changes led to the modern syndrome of social jetlag, a misalignment between circadian and social time. In most of us, the circadian clock is so delayed that we have to interrupt our natural sleep with an alarm clock to be awake for work/school schedules. Shift-workers suffer from the most extreme form of social jetlag. A growing body of studies show that this misalignment is associated with health deficits including various metabolic, cardiovascular and psychiatric syndromes and even increased cancer risks.

Early school times fundamentally clash with the late sleep of teenagers. This mismatch results in chronic sleep deprivation, which poses acute and long-term health risks and impairs students’ learning. Despite conclusive evidence that delaying school times has immediate benefits for sleep, the long-term effects on sleep are unresolved due to a shortage of longitudinal data. Here, we studied whether a flexible school start system, with the daily choice of an 8AM or 08:50AM-start, allowed secondary school students to improve their sleep and psychological functioning in a longitudinal pre-post design over exactly 1 year. Based on 2 waves, each with 6-9 weeks of daily sleep diary, we found that students maintained their 1-hour-sleep gain on days with later starts, both longitudinally (n=28) and cross-sectionally (n=79). This sleep gain was independent of chronotype and frequency of later starts but differed between genders. Girls were more successful in keeping early sleep onsets despite later sleep offsets, whereas boys delayed their onsets and thus had reduced sleep gains after 1 year. Students also reported psychological benefits (n=93), increased sleep quality and reduced alarm-driven waking on later school days. Despite these benefits on later schooldays, overall sleep duration was not extended in the flexible system. This was likely due to the persistently low uptake of the late-start option. If uptake can be further promoted, the flexible system is an appealing alternative to a fixed delay of school starts owing to possible circadian advantages (speculatively through prevention of phase-delays) and psychological mechanisms (e.g. sense of control).Significance statementTeenage sleep becomes progressively later during adolescence but school starts do not accommodate this shifted sleep window. This mismatch results in chronic sleep deprivation in teenagers worldwide, which is a pervasive public health concern. Delaying school starts could counteract this misalignment if students keep sleep onsets stable. However, few studies have investigated long-term effects of delayed starts on sleep. We observed here that students slept persistently longer and better when school started later in a flexible start system. Girls were especially successful in keeping stable onsets. Students also benefitted psychologically and liked the flexible system despite only a modest uptake of later starts. The flexible system is an interesting alternative to a fixed delay and should receive more scientific attention.

Kaum jemand hat den Schlaf so umfassend erforscht wie Till Roenneberg. Im Interview mit intensiv-Herausgeberin Rita Wegmann hat sich der Chronobiologe und Schlafforscher unseren Fragen gestellt.

Die herrschenden Sommerzeitregelungen werden kontinentubergreifend neu diskutiert. Wahrend das bisher „Sommerzeit-freie“ Japan diese zweimal jahrliche Intervention einzufuhren plant, mochten andere Regionen die Uhrenumstellungen abschaffen – allerdings mit unterschiedlichen Ansatzen: Kalifornien setzt auf ganzjahrige Sommerzeit, die EU-hat sich noch nicht zwischen den Optionen ganzjahrige Standard- oder Sommerzeit entschieden und will die Entscheidung 2020 den Mitgliedsstaaten uberlassen. Eng im Zusammenhang mit diesen Zeitkonstruktionen steht auch die Entscheidung, zu welcher Zeitzone ein Land gehort. Wenn man die Biologie versteht, die diese politischen Entscheidungen begleitet, wird man feststellen, dass Uhrenumstellungen und Zeitzonenwechsel auf das Gleiche hinauslaufen und dass sich diese Konstruktionen auf unsere Gesundheit auswirken. Aus diesen Grunden sollte man die zugrundeliegende Chronobiologie verstehen, bevor man in Sachen Sommerzeit oder Zeitzonen Gesetze verabschiedet.

Publisher's version (útgefin grein)., Both short and long sleep are associated with an adverse lipid profile, likely through different biological pathways. To elucidate the biology of sleep-associated adverse lipid profile, we conduct multi-ancestry genome-wide sleep-SNP interaction analyses on three lipid traits (HDL-c, LDL-c and triglycerides). In the total study sample (discovery + replication) of 126,926 individuals from 5 different ancestry groups, when considering either long or short total sleep time interactions in joint analyses, we identify 49 previously unreported lipid loci, and 10 additional previously unreported lipid loci in a restricted sample of European-ancestry cohorts. In addition, we identify new gene-sleep interactions for known lipid loci such as LPL and PCSK9. The previously unreported lipid loci have a modest explained variance in lipid levels: most notable, gene-short-sleep interactions explain 4.25% of the variance in triglyceride level. Collectively, these findings contribute to our understanding of the biological mechanisms involved in sleep-associated adverse lipid profiles., This project was supported by a grant from the US National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (R01HL118305). This research was supported in part by the Intramural Research Program of the National Human Genome Research Institute, National Institutes of Health. Tuomas O. Kilpeläinen was supported by the Danish Council for Independent Research (DFF–6110-00183) and the Novo Nordisk Foundation (NNF18CC0034900, NNF17OC0026848 and NNF15CC0018486). Diana van Heemst was supported by the European Commission funded project HUMAN (Health-2013-INNOVATION-1-602757). Susan Redline was supported in part by NIH R35HL135818 and HL11338. Study-specific acknowledgements can be found in the Supplementary Notes 2 and 4. The data on coronary artery disease have been contributed by the Myocardial Infarction Genetics and CARDIoGRAM investigators, and have been downloaded from www.CARDIOGRAMPLUSC4D.ORG.

Chronobiology is a thriving research field that spans all biomedical disciplines ranging from molecular biology and metabolism to psychology and internal medicine. Circadian rhythms are generated at the molecular level in practically all cells of the body. This ensemble of clocks forms the "circadian system" that coordinates every aspect of our biology on a daily basis-from the cells, tissues and organs up to the concerted regulation of metabolism or higher functions like sleep-wake behaviour, immune responses or cognition. With the help of a "master clock" in the brain, the mammalian circadian system actively synchronises (entrains) to light and darkness via the eyes. Industrialisation and urbanisation have drastically changed the way we expose ourselves to light and darkness and consequently how our clocks entrain. These changes led to the modern syndrome of social jetlag, a misalignment between circadian and social time. In most of us, the circadian clock is so delayed that we have to interrupt our natural sleep with an alarm clock to be awake for work/school schedules. Shift-workers suffer from the most extreme form of social jetlag. A growing body of studies show that this misalignment is associated with health deficits including various metabolic, cardiovascular and psychiatric syndromes and even increased cancer risks.

Previous studies have reported a shift in the timing of sleep during adolescence toward a later time. To date, it is unclear whether hormonal changes during puberty might contribute to this change in sleeping behavior. We systematically assessed pubertal development and sleep timing in a cross-sectional case-control study in girls with precocious (n = 42) and boys with delayed pubertal development (n = 19). We used the Munich ChronoType Questionnaire and the Children&rsquo, s ChronoType Questionnaire to assess sleep timing in patients and age- and sex-matched controls (n = 309) and used the midpoint of sleep on free days, corrected for potential sleep debt accumulated during the school week, as a marker for sleep timing. Compared to the controls, girls with central precocious puberty showed a delay in sleep timing of 54 min, and girls with premature pubarche slept on average 30 min later. Male adolescents with delayed pubertal development showed an average sleep midpoint that was 40 min earlier compared to the control group. The results of this pilot study suggest an association between pubertal onset and shifts in sleep timing, which is a novel finding in human sleep behavior. Prospective studies in larger cohorts will be needed to examine the robustness and generalizability of the findings.

Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Fundação para a Ciência e Tecnologia (FCT) and Fundo Social Europeu (FSE) Introduction Atypical work schedules encompass more than 20% of the European workforce. The link between shift work and cardiovascular disease (CVD) has been extensively studied being lifestyle behaviours, sleep disruption and circadian misalignment the key mechanisms involved. Social Jetlag (SJL) has been proposed as a proxy for circadian misalignment in epidemiological studies, once it takes into account individual’s chronotype and working schedules. Therefore we hypothesize that, among workers under fixed atypical work schedules, those with a greater SJL have a higher CVD risk. Methods A cross-sectional observational study was conducted among blue-collar workers of one retail company. Fixed working schedules were early morning, late evening, and night work. Sociodemographic, occupational, lifestyle and sleep data were collected through questionnaire. SJL was quantified by the difference for mid-sleep points on work- and free-days. Even though SJL is a continuous variable, 3 categories have been used (≤2h; 2-4h; ≥4h). Blood pressure (BP) and the total cholesterol (TC) were assessed. The CVD risk was estimated according to the relative risk SCORE chart. A relative risk≥3 was considered "high CVD risk". Descriptive statistics and bivariate analysis according to the CVD risk (high vs other) was performed. The relationship between SJL and high CVD risk was analysed through logistic binary regression using generalized linear models adjusted for age, sex, education, Body Mass Index, consumptions, sleep duration and quality plus work schedule and seniority. Results Of the 301 workers, 56.1% were male with a mean age of 33.0 ± 9.4years. Average SJL was 1:57 ± 1:38hours with the majority of workers experiencing ≤2h (59.4%) and 8% (n = 24) more than 4h. Less than a half had hypercholesterolemia (48.8%), overweight (37.9%)or hypertensive values (10.6%), however 50.5% were currently smokers. We found a significant trend for hypertension (p = 0.006) and smoking prevalence (p = 0.043) among ordinal SJL categories. A relative "high CVD risk" was found in 20.3% of the sample (n = 61). These workers were significantly older (p Conclusions We found compelling evidence that a greater SJL was associated with a bigger chance of high CVD risk. From this innovative perspective, the focus is not just on the working schedule itself but also on the worker’s chronotype. These findings suggest that interventions aimed to reduce Social Jetlag, especially in extreme chronotypes and working schedules, poses a great opportunity to minimize the cardiovascular health impact of shift work.

Autonomously oscillating circadian clocks resonate with daily environmental (zeitgeber) rhythms to organize physiology around the solar day. While entrainment properties and mechanisms have been studied widely and in great detail for light-dark cycles, entrainment to daily temperature rhythms remains poorly understood despite that they are potent zeitgebers.Here we investigate the entrainment of the chronobiological model organism Neurospora crassa, subject to thermocycles of different periods and fractions of warm versus cold phases, mimicking seasonal variations. Depending on the properties of these thermocycles, regularly entrained rhythms, period-doubling (frequency demultiplication) but also irregular aperiodic behavior occurs. We demonstrate that the complex nonlinear phenomena of experimentally observed entrainment dynamics can be understood by molecular mathematical modeling.Abstract Figure

© 2021 The Authors. Journal of Sleep Research published by John Wiley & Sons Ltd on behalf of European Sleep Research Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., Cardiovascular diseases cause >4 million deaths each year in Europe alone. Preventive approaches that do not only consider individual risk factors but their interaction, such as the Systematic COronary Risk Evaluation (SCORE), are recommended by European guidelines. Increased cardiovascular risk is associated with shift-work, surely interacting with the concurrent conditions: disruption of sleep, unhealthy behaviours, and circadian misalignment. Social jetlag (SJL) has been proposed as a way to quantify circadian misalignment. We therefore investigated the association between SJL and cardiovascular health in a cross-sectional observational study involving blue-collar workers, who either worked permanent morning, evening, or night shifts. Sociodemographic, health and productivity data were collected through questionnaires. Blood pressure and cholesterol were measured and the cardiovascular risk was estimated according to the relative risk SCORE chart. Bivariate analysis was performed according to the cardiovascular risk and the relationship between SJL and high cardiovascular risk was analysed through logistic regression. Cumulative models were performed, adjusted for various confounding factors. After 49 exclusions, the final sample comprised 301 workers (56% males; aged 30% (odds ratio 1.31, 95% confidence interval 1.02-1.68). This is the first study indicating that SJL potentially increases cardiovascular risk, and suggests that sleep and individual circadian qualities are critical in preventing negative health impacts of shift-work., This work was supported by the PhD research Grant PDE/BDE/127787/2016 from Fundação para a Ciência e Tecnologia/Fundo Social Europeu.

© The Author(s) 2020. Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/, In humans, sleep regulation is tightly linked to social times that assign local time to events, such as school, work, or meals. The impact of these social times, collectively-social time pressure, on sleep has been studied epidemiologically via quantification of the discrepancy between sleep times on workdays and those on work-free days. This discrepancy is known as the social jetlag (SJL). COVID-19-mandated social restrictions (SR) constituted a global intervention by affecting social times worldwide. We launched a Global Chrono Corona Survey (GCCS) that queried sleep-wake times before and during SR (preSR and inSR). 11,431 adults from 40 countries responded between April 4 and May 6, 2020. The final sample consisted of 7517 respondents (68.2% females), who had been 32.7 ± 9.1 (mean ± sd) days under SR. SR led to robust changes: mid-sleep time on workdays and free days was delayed by 50 and 22 min, respectively; sleep duration increased on workdays by 26 min but shortened by 9 min on free days; SJL decreased by ~ 30 min. On workdays inSR, sleep-wake times in most people approached those of their preSR free days. Changes in sleep duration and SJL correlated with inSR-use of alarm clocks and were larger in young adults. The data indicate a massive sleep deficit under pre-pandemic social time pressure, provide insights to the actual sleep need of different age-groups and suggest that tolerable SJL is about 20 min. Relaxed social time pressure promotes more sleep, smaller SJL and reduced use of alarm clocks.

With the emergence of big data science, the question how we can easily collect meaningful information about circadian clock phenotypes in large human cohorts imposes itself. Here, we describe potentials and limitations of using questionnaires, specifically the Munich ChronoType Questionnaire (MCTQ), to characterize such circadian phenotypes. We also discuss scenarios when alternative methods might be more appropriate.

With the emergence of big data science, the question how we can easily collect meaningful information about circadian clock phenotypes in large human cohorts imposes itself. Here, we describe potentials and limitations of using questionnaires, specifically the Munich ChronoType Questionnaire (MCTQ), to characterize such circadian phenotypes. We also discuss scenarios when alternative methods might be more appropriate.

Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Current patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and emerging lighting technologies now present opportunities to adjust lighting to promote optimal physical and mental health and performance. A newly developed, SI-compliant standard provides a way of quantifying the influence of light on the intrinsically photosensitive, melanopsin-expressing, retinal neurons that mediate these effects. The present report provides recommendations for lighting, based on an expert-scientific consensus and expressed according to this new measurement standard. These recommendations are supported by a comprehensive analysis of the sensitivity of human ‘non-visual’ responses to ocular light, are centred on an easily measured quantity (melanopic equivalent daylight (D65) illuminance), and provide a straightforward framework to inform lighting design and practice.

Long and short sleep duration are associated with elevated blood pressure (BP), possibly through effects on molecular pathways that influence neuroendocrine and vascular systems. To gain new insights into the genetic basis of sleep-related BP variation, we performed genome-wide gene by short or long sleep duration interaction analyses on four BP traits (systolic BP, diastolic BP, mean arterial pressure, and pulse pressure) across five ancestry groups using 1 degree of freedom (1df) interaction and 2df joint tests. Primary multi-ancestry analyses in 62,969 individuals in stage 1 identified 3 novel loci that were replicated in an additional 59,296 individuals in stage 2, including rs7955964 (FIGNL2/ANKRD33) showing significant 1df interactions with long sleep duration and rs73493041 (SNORA26/C9orf170) and rs10406644 (KCTD15/LSM14A) showing significant 1df interactions with short sleep duration (Pint < 5×10−8). Secondary ancestry-specific two-stage analyses and combined stage 1 and 2 analyses additionally identified 23 novel loci that need external replication, including 3 and 5 loci showing significant 1df interactions with long and short sleep duration, respectively (Pint < 5×10−8). Multiple genes mapped to our 26 novel loci have known functions in sleep-wake regulation, nervous and cardiometabolic systems. We also identified new gene by long sleep interactions near five known BP loci (≤1Mb) including NME7, FAM208A, MKLN1, CEP164, and RGL3/ELAVL3 (Pint < 5×10−8). This study indicates that sleep and primary mechanisms regulating BP may interact to elevate BP level, suggesting novel insights into sleep-related BP regulation.

This chapter summarizes epidemiological insights into sleep and wake behaviour and covers the limited knowledge about its disorders, with special emphasis on psychiatry. The chapter systematically refers to the interdependencies of four different aspects in both sleep and wake: timing, duration, structure, and quality. It provides an overview of the current methods used in the field for studying this behaviour and predicts that long-term actimetry monitoring in everyday life will revolutionize research into both sleep and the circadian clock. The chapter argues that a stronger alliance between sleep research and circadian biology will help to better understand the different aetiologies of sleep disorders, as well as the relationships between sleep and disease. It is predicted that strengthening our consideration of sleep’s circadian regulation versus its societal constraints—together with improved light environments—will ameliorate many sleep problems. There is also a need to improve public education about sleep and the circadian clock to increase self-awareness of sleep, activity, and light behaviour on an individual level to prevent false self-diagnoses due to misconceptions about sleep.