Health and legal time

Background Social jetlag (SJL) occurs in adolescents due to misalignment of the biological and social clocks, so that most teens wake up earlier than their biological clocks on weekdays and delay bedtime and wake up time on weekends. This shift in sleep timing among adolescents i…

Background Social jetlag (SJL) occurs in adolescents due to misalignment of the biological and social clocks, so that most teens wake up earlier than their biological clocks on weekdays and delay bedtime and wake up time on weekends. This shift in sleep timing among adolescents is associated with an adverse endocrine and behavioral risk profile, in addition to increased food consumption and increased body mass index (BMI). Objective The aim of this study was to determine the association between SJL, and the frequency of consumption of multiple food and beverage groups and BMI percentile in adolescents. Design Publicly available data from the cross-sectional Family Life, Activity, Sun, Health, and Eating (FLASHE) study were analyzed. Participants Participants from the FLASHE study were recruited from all regions of the United States between April and October 2014. Among the 1,581 adolescents aged 12 through 17 years in the original study, 1,556 with complete sleep data were analyzed. Main outcome measures The difference between the frequency of dietary consumption according to the Dietary Screener Questionnaire and BMI percentile was assessed in adolescents grouped according to SJL, as follows: no SJL: less than 1-hour difference; mild SJL: 1- to 2-hour difference; and severe SJL: more than 2-hour difference. Statistical analyses performed Differences in the frequency of food consumption were analyzed using the Kruskal-Wallis test. Secondary outcomes were analyzed using logistic regression models. Results Daily consumption frequency of sugar-sweetened beverages and fruits and vegetables differed among the 3 groups. Likewise, the BMI percentile differed among the 3 groups and was highest in the severe SJL group. Those in the severe SJL group had a 1.84-fold higher probability of having overweight or obesity (95% CI 1.83 to 1.84) than those in the no SJL group. Conclusions Severe SJL is associated with a higher frequency of sugar-sweetened beverage consumption and higher odds of having overweight or obesity compared with no SJL in adolescents.

With the disappearance of daylight saving time in 2021, chronobiologists advocate in an opinion piece in "Le Monde" adopting "standard" time, which resynchronizes the circadian rhythm.

Local and national governments around the world are currently considering the elimination of the annual switch to and from Daylight Saving Time (DST). As an international organization of scientists dedicated to studying circadian and other biological rhythms, the Society for Rese…

Local and national governments around the world are currently considering the elimination of the annual switch to and from Daylight Saving Time (DST). As an international organization of scientists dedicated to studying circadian and other biological rhythms, the Society for Research on Biological Rhythms (SRBR) engaged experts in the field to write a Position Paper on the consequences of choosing to live on DST or Standard Time (ST). The authors take the position that, based on comparisons of large populations living in DST or ST or on western versus eastern edges of time zones, the advantages of permanent ST outweigh switching to DST annually or permanently. Four peer reviewers provided expert critiques of the initial submission, and the SRBR Executive Board approved the revised manuscript as a Position Paper to help educate the public in their evaluation of current legislative actions to end DST.

The rapid evolution into a 24 h society challenges individuals’ ability to conciliate work schedules and biological needs. Epidemiological research suggests that social and biological time are increasingly drifting apart (“social jetlag”). This study uses a spatial regression dis…

The rapid evolution into a 24 h society challenges individuals’ ability to conciliate work schedules and biological needs. Epidemiological research suggests that social and biological time are increasingly drifting apart (“social jetlag”). This study uses a spatial regression discontinuity design to estimate the economic cost of the misalignment between social and biological rhythms arising at the border of a time-zone in the presence of relatively rigid social schedules (e.g., work and school schedules). Exploiting the discontinuity in the timing of natural light at a time-zone boundary, we find that an extra hour of natural light in the evening reduces sleep duration by an average of 19 minutes and increases the likelihood of reporting insufficient sleep. Using data drawn from the Centers for Disease Control and Prevention and the US Census, we find that the discontinuity in the timing of natural light has significant effects on health outcomes typically associated with circadian rhythms disruptions (e.g., obesity, diabetes, cardiovascular diseases, and breast cancer) and economic performance (per capita income). We provide a lower bound estimate of the health care costs and productivity losses associated with these effects.