ABOUT DAY CLOCK(CIRCADIAN) -CHANGE INDIVIDUAL; Lesson

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Kishor Kumar Seth

8th August 2021

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“EARLY BIRD AND NIGHT OWL”

INTRODUCTION;

ABOUT A DAY CLOCK(CIRCADIAN) -CHANGE INDIVIDUAL; Lesson

circadian clocks become misaligned with the new time and may take several days to adjust. Chronic circadian misalignment, e.g., as a result of shift work, has been shown to lead to several physical andmental health problems. Despite the serious health implications of circadian misalignment, relatively little is known about how genetic variation affects an individual’s ability to entrain to abrupt external changes. Accordingly, we used the one-hour advance from the onset of daylight saving time (DST)as a natural experiment to comprehensively study how individual heterogeneity affects the shift of sleep/wake cycles in response to an abrupt external time change. We found that individuals genetically predisposed to a morning tendency adjusted to the advance in a few days, while genetically predisposed evening-inclined individuals had not shifted.[1]

Genomic affect and daylight saving time{DST}

This study provides evidence that individuals respond differently when using different timing systems relative of other factors such as sleep duration, temperature, and physical activity level within their daily routines (e in-depth review ). Importantly this data could also be used for predicting individual responses among groups based on those which are most variable with respect two variables related with circadian rhythm change: light hours/day at night or environmental lighting, i e sunlight exposure during work times vs ambient room conditions. SOME STUDY PROVIDES{2}

Morning population shifts to the new time in three days while the evening population has notshifted 1 week after DST
Sleep midpoint in the morning group is signifcantly earlier than that in the evening group.
Evening population sleeps signifcantly less on work nights following DST relative to the week BEFORE
Social jet lag signifcantly increases in the evening population the week after DST{3}
FIGURE -A

SLEEP MIDPOINT ARE SIGNIFICANTALY DIFFERENT IN TWO GROUPS

In particular, recent work has revealed genetic associations with sleep midpoint, as objectively measured from accelerometers, rather than biased self-reported sleep information24. validated and objective genetic sleep midpoint association provide measure to characterize an individual’s genomic predisposition to morning ness or evening ness, specifically as it relates to the sleep/wake cycle. Here, we use the one-hour advance from the onset of daylight saving time as a natural experiment to com-prehensively study how heterogeneity affects an individual’s ability to entrain to an abrupt external time change. In total, from a cohort of 831 medicalinterns27with genotype information, we analisze thousands of sleep events the week before and the week after DST onset in 2019. After analysis, we see that morning-inclined individual sad just more rapidly to the time shift than evening-inclined. Moreover, evening-inclined individuals the week after DST. Ultimately, our results provide a more comprehensive evaluation of how genetic pre dispositions affect how the sleep/wake cycle patterns shift in response to an external change. Since DST is only a one-hour advance, observing differential effects by genetic disposition underscores the importance of heterogeneity in more extreme cases such as shift work. Additionally, our results further establish the utility of the polygenic score as a surrogate measure of phenotypes. Finally, understanding how subtle phenotypic differences affect shifting patterns will help inform individuals on how to prepare for abrupt external shifts , and ultimately, understanding of circadian mis alignment. Results Sleep midpoint in the morning group is significantly earlier than that in the evening group. We used the Objective Sleep Midpoint polygenic score (OSM PGS), calculated using a genome-wide chrono type genetic analysis of 85,670individuals24, as an objective measure for chronotype rather than subjective self report. Specifically, we calculated the OSM PGS with the methods describedpreviously29,30for all subjects with genetic information. As a higher OSM PGS corresponds to a later sleep midpoint, we divided all PGS scores into three quantiles and characterized the top quantile as an evening group and the bottom quantile as a morning group. Using all the sleep events up to the onset of DST, we plot the distribution of sleep midpoints for the morning and evening groups both on free nights. As expected, the morning group had significantly earlier sleep midpoints on both free and worknights, and the evening group displayed later sleep midpoints . Evening population sleeps significantly less on work nights following DST relative to the week before. For the week before and after DST onset, we computed the mean time asleep, in minutes, for night-time sleep events on Sunday-Thursday (work) nights for both the morning and evening groups . We saw a marginal decrease in the average time asleep in the morning population (mean 412.9±3 min before and408.5±2.9 min after ). In contrast, the mean time asleep decreased in the evening population (from411.6±2.97 min before to forward. Figure 1.Sleep midpoints are significantly different in the two group.

SOCIAL JET LEG IS SIGNIFICANTELY IN EVENING POPULATION AFER DST;

FIGURE-B

CONCLUTION.

The sleep timing of the morning population realigned to the sleep schedule before DST. Given that the experimental setting was everyday life with several external and environmental signals, we cannot completely rule out the possibility that this realignment is due to masking rather than entrainment. Related ABOUT DAY CLOCK(CIRCADIAN) -CHANGE INDIVIDUAL; THIS IS TRUE- Lesson

FIGURE-3