Effects of the COVID-19 lockdown on human sleep and rest-activity rhythms

Abstract

In modern societies, human rest-activity rhythms and sleep result from the tensions and dynamics between the conflicting poles of external social time (e.g., work hours and leisure activities) and an individual's internal biological time. A mismatch between the two has been suggested to induce 'social jetlag' [1] and 'social sleep restriction', that is, shifts in sleep timing and differences in sleep duration between work days and free days. Social jetlag [2,3] and sleep restrictions [4] have repeatedly been associated with negative consequences on health, mental wellbeing, and performance. In a large-scale quasi-experimental design, we investigated the effects of the phase with the most rigorous COVID-19 restrictions on the relationship between social and biological rhythms as well as sleep during a six-week period (mid-March until end of April 2020) in three European societies (Austria, Germany, Switzerland). We found that, on one hand, the restrictions reduced the mismatch between external (social) and internal (biological) sleep-wake timing, as indexed by significant reductions in social jetlag and social sleep restriction, with a concomitant increase in sleep duration. Sleep quality on the other hand was slightly reduced. The improved individual sleep-wake timing can presumably be attributed to an increased flexibility of social schedules, for instance due to more work being accomplished from home. However, this unprecedented situation also led to a significant increase in self-perceived burden, which was attendant to the decrease in sleep quality. These adverse effects may be alleviated by exposure to natural daylight as well as physical exercise.

Figure 1

Effects of the ‘lockdown’ on social jetlag, social sleep restriction, sleep duration, and sleep quality. Social jetlag (i.e., the difference between mid-sleep on free days and work days) is reduced by 13 minutes (A), and social sleep restriction (i.e., the difference in sleep duration between free days and work days) by 25 minutes (B). Sleep duration is increased by 13 minutes (C) while sleep quality (higher values denote decreased sleep quality) is reduced by 0.25 points on a scale from 0–25 (D). Reported differences are interpolated medians of individual differences. Each plot depicts the probability density of the data on top of a boxplot with overlying individual data points. Boxplots: lower and upper hinges correspond to the first and third quartiles (the 25th and 75th percentiles) and the thick vertical line in the box corresponds to the median. The upper (lower) whisker extends from the hinge to the largest (smallest) value no further than 1.5 ^∗ inter-quartile range (IQR, or distance between the first and third quartiles).