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.

No abstract

The daily rhythm of feeding-fasting and meal-timing are emerging as important determinants of health. Circadian rhythm research in animal models and retrospective analyses of human nutrition data have shown that reduced length of overnight fasting or increased late night eating increases risk for metabolic diseases including obesity and diabetes. However, the daily rhythm in eating pattern in humans is rarely measured. Traditional methods to collect nutrition information through food diary and food log pay little attention to the timing of eating which may also change from day to day. We adopted a novel cell-phone based approach to longitudinally record all events of food and beverage intake in adults. In a feasibility study daily food-eating patterns of 93 healthy individuals were recorded for 21 days using camera phones. Analysis of the daily eating patterns of these individuals indicates deviation from conventional assumption that people eat three meals-a-day within a 12 h interval. We found that eating events are widespread throughout the day, with <30% of calories consumed before noon and >30% consumed in evening and late night hours. There was little difference in eating pattern between weekdays and weekends. In this cohort more than 50% of people spread their caloric intake events over 15 h or longer. One decile of the cohort who were spouses of shift-workers or had flexible work schedule spread their caloric intake over 20 h. Although the nutrition quality and diversity of food consumed is different between South-East Asian and Western countries, such overall disruption of daily eating-fasting rhythm is similar. Therefore, in view of hypothesis that disrupted daily eating pattern may contribute to the global increase in metabolic diseases and modification of daily eating pattern is a potential modifiable behavior to contain these diseases, monitoring eating pattern is an important aspect of lifestyle.

BackgroundMany vertebrates distinguish between short and long day lengths using suprachiasmatic nuclei (SCN). In birds particular, the mediobasal hypothalamus (MBH) is suggested to be involved in the timing of seasonal reproduction. This study investigated the response of SCN and MBH to a single long day, and the role of MBH in induction of the migratory phenotype in night-migratory blackheaded buntings.Methodology/Principal FindingsExperiment 1 immunocytochemically measured c-fos in the SCN, and c-fos, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) in the MBH of buntings exposed to a 20 h light period. Long light period induced significantly stronger c-fos expression, measured as number of c-fos-like immunoreactive (c-fos-lir) cells, in MBH, but not in the SCN. Within the MBH, c-fos-lir cells were significantly denser in the inferior hypothalamic nucleus (IH) and infundibular nucleus (IN), but not in the dorsomedial hypothalamus (DMH). IH and IN also had significantly increased number of VIP and NPY labeled cells. DMH had significantly increased number of VIP labeled cells only. Experiment 2 assayed c-fos, VIP and NPY immunoreactivities in the middle of day and night in the MBH of buntings, after seven long days (day active, non-migratory state) and after seven days of Zugunruhe (night active, migratory state) in long days. In the migratory state, the number of c-fos-lir cells was significantly greater only in DMH; VIP-lir cells were denser in all three MBH regions suggesting enhanced light sensitivity at night. The denser NPY-lir cells only in IN in the non-migratory state were probably due to premigratory hyperphagia.Conclusions/SignificanceIn buntings, SCN may not be involved in the photoperiod-induced seasonal responses. MBH contains the seasonal clock sensitive to day length. VIP and NPY are parts of the neuroendocrine mechanism(s) involved, respectively, in sensing and translating the photoperiodic message in a seasonal response.

We hypothesized differences in molecular strategies for similar journeys that migrants undertake to reproduce in spring and to overwinter in autumn. We tested this in redheaded buntings () photoinduced into spring and autumn migratory states, with winter and summer non-migratory states as controls. Compared with controls, buntings fattened, gained weight and showed (nocturnal migratory restlessness) in the migratory state. Spring migration was associated with greater fat and body mass, and higher intensity of, compared with autumn migration. Circulating corticosterone levels were higher in spring, while T3 levels were higher in autumn. Hypothalamic expression of thyroid hormone-responsive (, ), light-responsive (, ,) and (tyrosine hydroxylase, involved in dopamine biosynthesis) genes showed significant changes with transition from non-migratory to the migratory state. There were significantly higher mRNA expressions in autumn, except for higher levels in the spring. Furthermore, the expression patterns of (not) and genes suggested an epigenetic difference between the non-migrant and migrant periods, and the spring and autumn migrant periods. These results demonstrate for the first time seasonal transition in hypothalamic gene expressions, and suggest differences in regulatory strategies at the transcriptional level for spring and autumn migrations in songbirds.