Anyone who has ever travelled across multiple time zones may be familiar with the concept of jetlag. When this occurs, your internal biological clock is thrown off and no longer aligns with your external activities.
However, travel-related jetlag is not the only form of jetlag. For many people, a rigid work schedule during the week contrasts with a more relaxed schedule on weekends. This can result in differences in sleep timing and duration between work days and rest days. These jetlag-like effects on sleep patterns are often referred to as social jetlag and social sleep restrictions. A new study published in the journal Current Biology explores the impact of the COVID-19 lockdown measures on these phenomena(1).
To do this, the study authors conducted a semi-experimental survey. The survey recruited individuals from three countries with strict lockdown measures (Austria, Germany, and Switzerland). The participants were asked to record details of their sleep quality and duration for four weeks from March 23rd to April 26th, a period that corresponded with the strictest lockdown measures in these respective countries.
In total, 435 individuals completed the survey. The main outcomes of interest were self-reported sleep quality, any differences in sleep duration between work days and rest days and a questionnaire to assess social jetlag based on differences between the midpoint of a night’s sleep on working days compared to rest days. The survey also captured information on life satisfaction and some background information on the participants. Participants were asked to answer many questions twice. Firstly, recalling their pre-lockdown lifestyle and secondly to answer the same questions in light of current lockdown restrictions.
The main findings of the survey revealed that the lockdown measures had a beneficial effect on sleep duration but a harmful effect on sleep quality. The authors used the difference in midpoint as a measure of social jetlag and found that the gap between midpoints on working days versus rest days was reduced by 13 minutes during the lockdown. Social sleep restriction was assessed by the difference in sleep duration between work days and rest days. This difference was on average about 25 minutes less during lockdown than in the pre lockdown phase. These results suggest the lockdown brought about a more regular sleeping pattern.
The authors assign much of this improvement to the increases in working from home as a result of the lockdown. Working from home increases flexibility in working hours and results in a less rigid balance between working hours and leisure/rest hours. However, sleep quality overall was found to have declined during the lockdown. The study authors tie this to a decrease in overall mental and physical well-being observed during the lockdown and suggest that increasing exposure to daylight and level of exercise could alleviate this quality reduction.
There are a number of limitations to this study. The study sampling and demographic details of the respondents limit the broader validity of the results. For example, over three quarters of the participants were women (327) whilst almost two-thirds were ages between 18 and 35 years. Crucially, participants were asked to retrospectively answer many of the questions about their pre-lockdown sleep and behavioural habits. This represents a further weakness in the study as these recollections are subject to various risks of bias.
Overall however, the study does raise some important issues. The sudden nature of the lockdown has forced dramatic routine change upon a huge number of people across the world. Whilst further research is needed, this study does suggest that sleep quality and overall life satisfaction have been negatively impacted by the COVID-19 lockdown measures.
Written by Michael McCarthy
1. Blume C, Schmidt MH, Cajochen C. Effects of the COVID-19 lockdown on human sleep and rest-activity rhythms. Curr Biol. 2020.
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