Retirement Increases Social and Biological Sleep Clock Alignment Across Lifespan

Social jetlag (SJL) decreases across the lifespan, with a pronounced reduction post-retirement even after accounting for behavioral factors. These findings were recently published in the Journal of Sleep Research.

SJL is the misalignment between the internal biological and external conventional clocks, which may result in deleterious health effects. However, this relationship is limited to low quality evidence, such as self-reported methods and cross-sectional studies.

In this prospective analysis, researchers aimed to understand the impact of work demands and lifestyle changes on sleep patterns. The researchers assessed the relationship between SJL across the lifespan with age as a continuous variable. The association between SJL and work cessation was also examined. Lastly, the researchers evaluated the impact of self-reported chronotype, daily average caffeine intake, alcohol, and stress on social jetlag.

Participants used a validated sleep study SleepScore mobile application to monitor movements and respiration in bed. Users with at least 20 weekday and eight weekend recordings were selected for inclusion. SJL was defined as the difference between weekday and weekend overall mean mid sleep times and measured in minutes.

In the final sample, there were 2439 participants, across 500,415 nights. Participants had a mean (SD) age of 52.5 (16) years and 52% were women.

In a sub-group analysis, the investigators included 599 participants with a mean age of 60.5 (SD=2.9) years as proxies for the pre-retirement group and 442 participants with a mean age of 69.9 (SD=2.8) years for the post-retirement group.

The post-retirement group had lower SJL than the pre-retirement group and the full sample of participants (all P<.0001). Compared to the pre-retirement group, however, the post-retired participants experienced lower average sleep efficiency and more problems staying asleep (all P<.001).

In contrast to the weekdays, pre-retired and retired participants delayed their sleep and wake times on the weekends, with an increase in total sleep time for both groups. Pre-retired participants had more problems staying asleep on the weekends (P=.015).

There was a significant negative association between age and SJL (t = -9.90; P<.001), with each additional year corresponding to a 0.64 min decrease in SJL. When the researchers included self-reported chronotype, stress, caffeine, and alcohol, the explanatory power of the models slightly increased. However, the effect of age remained consistent (t = -8.91; P<.0001).

This SJL reduction was most evident in post-retired participants with strong morning chronotypes (t= -4.324; P<.001). However, pairwise comparisons did not detect statistically significant differences between chronotypes (P>.05).

The study authors concluded, “These findings suggest that age remains a consistent and significant predictor of reduced social jetlag, even when accounting for additional behavioral factors.”

Study limitations included the lack of causality between age, retirement, and SJL due to the short duration of the study; the possibility of inaccuracy, as age was used as a proxy for retirement; and limited generalizability and selection bias due to data collection from specific mobile app users.

Disclosure: Some study authors declared affiliations with SleepScore Labs.

This article originally appeared on Psychiatry Advisor