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Researchers in Europe and the United States studied the effects of both weekday and weekend sleep durations on mortality in Sweden.
We live in a sleep-deprived society, which is a serious issue, as inadequate sleep has been linked to increased mortality. Many people thus sleep in, or catch up on sleep, during the weekend. But does this compensating behaviour actually help? Can sleeping in on weekends make up for not sleeping enough during weekdays, and hence reduce mortality rates?
Examining weekend and weekday sleep
With this question in mind, researchers in Europe and the United States examined sleep duration data from a group of people in Sweden over 13 years, broken down by both weekend and weekday sleep. Indeed, the majority of sleep studies do not distinguish between weekend and weekday sleep but focus on average or “usual” sleep durations during the entire week. They published their results in the Journal of Sleep Research.
Looking at the effect of sleep on mortality 13 years later
The participants in this study were taken from the Swedish National March Cohort (SNMC). The National March was a 1997 fundraising event put on by the Swedish Cancer Society, and participants were invited to fill out a 32-page health questionnaire, including questions about their sleep habits.
The participants were asked the number of hours that they slept on both workdays and weekdays, and on days off, which would include weekends. The answer options were less than 5, 5, 6, 7, 8, or 9 or more hours. They defined short sleep as less than 5 hours and long sleep as 9 or more hours. The baseline or reference sleep time for the study was 7 hours. After exclusions for incomplete answers, the number of people whose data was used in this study was 38,015.
A follow-up was done 13 years later, in 2010, to examine which participants had died. At that time, 3,234 deaths had occurred, and this data was used to establish whether there was any relationship between weekday and weekend sleep habits and mortality.
Any associations between sleep duration and mortality occurred at ages under 65 years
They compared mortality results to the baseline of participants who slept seven hours a night. The major results were as follows:
- For participants under 65 years of age, short weekend sleep was associated with a 52% higher mortality rate.
- For participants under 65 years of age who slept 5 hours or less during both weekdays and weekends, a 65% higher mortality rate was observed.
- For participants aged under 65 years, sleeping longer durations on weekends after sleeping short durations on weekdays was not associated with increased mortality.
- A higher mortality risk was also seen in participants under 65 years of age who slept 9 hours or more during both weekdays and weekends.
- For participants aged over 65 years, no association was found between sleep duration and mortality.
- As age increased, the difference between weekday and weekend sleep durations decreased, and actually approached zero for participants over 65 years of age. Specifically, as participants aged, their weekday sleep duration stayed the same, while their weekend sleep duration gradually decreased.
The authors noted some study limitations. There is a possibility that respondents may have misinterpreted the phrase “day off”, and as sleep duration was self-reported and only at baseline, it was not possible to detect changes in sleep behaviour over time.
Sleeping in on weekends seems to help
The main application is that for people under 65 years of age, sleeping too little or too much on both weekdays and weekends increases one’s mortality risk. However, if these same people sleep longer on weekends after sleeping too little during the week, there appears to be a compensating effect. Thus, sleeping in on the weekend seems to have a real health benefit. More research is needed, of course, to determine an exact relationship.
Written by Raymond Quan, MASc, MBA
Reference: Akerstedt et al. “Sleep duration and mortality – Does weekend sleep matter?” J Sleep Res. 2018; e12712.