Sleep and circadian rhythms during the COVID-19 lockdown

Sleep is sensitive to many factors, including biological needs, the timing of the body’s circadian system, environmental lighting, social demands, stress, and overall health. It’s not surprising, then, that the effects of the COVID-19 pandemic and the resultant lockdowns increase sleep disturbance.

It turns out, though, that the situation is more complicated. Many people are sleeping more, though often finding it of poorer quality; it is actually reducing what is known as ‘social jet lag’; young adults may be particularly vulnerable to sleep disturbance; and problems may persist after the end of lockdown. Reports are starting to come in from around the world: let’s look at some of them.

Sleep and social jet lag: Many of us typically sleep less on weekdays than on weekends, when we may stay up later but don’t need an alarm clock, and can ‘sleep in’. The pattern, then, can be to become progressively sleep deprived during the workweek, and try to pay back this sleep debt, with slightly different timing, on the weekend. Till Roenneberg at the University of Munich coined the term ‘social jet lag’ for when this disparity becomes significant, and suggested that it might occur in two-thirds of the population (1). In a sense, it is as if a person flies from Paris to New York on Friday evenings, and returns on Monday. The repercussions from living out of phase with the environment are only beginning to be understood. One consequence of social jet lag—which involves both issues and timing and amount of sleep—can be an increased risk of becoming overweight or obese. It is also associated with smoking and mood changes, as well as increased consumption of alcohol and caffeine. Long term accumulation of a sleep debt from any reason has been associated as well with accidents, mood disorders, diabetes, and cardiovascular disease.

One intriguing aspect of the lockdown is that there may be a reduction in social jet lag. A study by Kenneth Wright of students at the University of Colorado after the lockdown found that they began to have more regular hours, and reported sleeping about 30 minutes more on weekdays and 24 minutes on weekends (2). A larger study by Christine Blume and colleagues of the general population in Austria, Germany, and Switzerland during lockdown in March and April 2020 found that many people are sleeping longer, perhaps 15 minutes, with less difference in weekdays and weekends (3). As she has pointed out, normally a reduction in social jet lag might be expected to give a sense of sleeping better, but in this case the tendency was to feel that sleep quality had deteriorated. One implication may be that the burden of anxiety and change in lifestyle may have a greater impact than the possible benefits of having less social jet lag.

Vulnerability to sleep disturbance, and effects of infection on sleep: A Chinese study of over 5000 persons in February 2020 stratified them according to degree of viral threat, ranging from inpatients with COVID-19 and their healthcare workers on one extreme to the general public away from epicenters who were affected primarily by lockdown and other safety measures (4). The overall frequency with insomnia as measured by the Insomnia Severity Index (ISI) was 20 percent, varying across groups directly with the degree of threat. Degree of dissatisfaction/satisfaction with sleep as well as symptoms of difficulty staying asleep and awakening early followed this pattern most closely. Other measures for symptoms of depression, anxiety, and stress also tracked proportionately to degree of threat. (It is important to recall that these are not diagnostic instruments but measures of symptoms.) Sleep symptoms were greatest in the young, particularly females located in the epicenter and exposed to higher degrees of threat.

A similar pattern was seen in 484 patients hospitalized in 2019 for COVID-19 in the Wuhan area (5). Significant amounts of insomnia as measured by the ISI were found in 42.8 percent, and tended to be among younger persons, particularly female, and not surprisingly those with higher anxiety and fatigue scores.

Sleep difficulties may persist after lockdown has ended: A study of 1015 Americans between 18 and 79 conducted by SleepStandards found that 67 percent felt that their sleep was less healthy after the lockdown (6). 53 percent felt they were sleeping less (which differs somewhat from the other studies). They tended to go to sleep earlier, though there was no comparison of weekdays and weekends. 68 percent described feeling stressed and having difficulty sleeping, which persisted after the end of the lockdown.

Summary: Clearly we don’t have enough information to make general conclusions about the impact of the pandemic on sleep, but some tentative themes are emerging. If these early studies are borne out as we learn more, the conclusions might be something like this: Many of us lead lives of partial sleep deprivation during work nights with a shift of timing and some catching up on non-work nights, and this appears to increase the risk for long-term health concerns. The release of many social constraints during the lockdown has actually allowed a small increase in sleep and a lessening of this ‘social jet lag’, but it seems possible that this potential benefit is outweighed by the effects of stress and anxiety. Sleep disturbance increases with the degree of threat of infection with COVID-19, as well as in infected persons, but surprisingly two studies suggest there may be greater vulnerability among young persons. And there is some evidence that sleep disturbance among healthy persons in lockdown may persist after restrictions are lifted.

It has been known for some time that acute insomnia related to stressors may take on a life of its own, perpetuated by unhelpful learned associations and anxiety about not sleeping (‘psychophysiologic insomnia’), and this may contribute as well to an ongoing problem even in better times. Insomnia itself is a risk factor for depression and a variety of health issues. There is also growing realization that among persons infected with COVID-19, there may be sequelae including cognitive and mood changes. These all suggest that it will be important to be aware that the consequences of COVID-19 and its preventive measures may go far beyond the obvious concerns of dealing with the acute infection.