New research is trying to put to bed the idea that too little sleep during weekdays can't be counteracted by a longer sleep during weekends.
A prospective cohort study of nearly 40,000 participants showed that, at least in those younger than 65 years, sleeping an average of 5 hours or fewer per night over the weekend increased mortality risk by 52% compared with sleeping 7 hours.
Having short sleep on both the weekdays and weekend, as well as having long sleep at both times, also increased the risk in this age group.
However, the mortality rate among participants with shorter sleep hours during weekdays and longer sleep hours during weekends did not differ significantly from those who averaged 7 hours per night consistently (the reference group).
"Possibly, long weekend sleep may compensate for short weekday sleep," write the investigators, led by Torbjörn Åkerstedt, PhD, Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden. But they note that more research is needed.
There were no significant associations between sleep and mortality risk in the participants aged 65 years or older.
The findings were published online May 22 in the Journal of Sleep Research.
"Previous studies have found a U-shaped relationship between mortality and (weekday) sleep duration," the investigators write. This means that "both short and long sleep is associated with higher mortality," they add.
However, they note that published findings have been inconsistent, especially when it comes to measuring weekday or weekend sleep specifically.
In the current study, the researchers assessed 43,880 participants in the Swedish National March Cohort, all of whom filled out a 36-page questionnaire on lifestyle and medical history. After exclusion criteria were applied, the final cohort of 38,015 individuals was followed for 13 years (October 1997 through December 2010) through linkage with databases, such as the Swedish National Register of Death.
The participants were also placed into subgroups based on average sleep duration at baseline, from "short" (≤5 hours/night) to "long" (≥9 hours/night). The reference group received 7 hours of sleep consistently.
In the younger than 65 years age group, the hazard ratio (HR) was 1.52 for those who slept an average of 5 hours or fewer per weekend night at baseline compared with those who slept an average of 7 hours per weekend night (95% confidence interval [CI], 1.15 - 2.02). There were no significant links between mortality risk and 9 hours or more of weekend sleep.
A 65% higher mortality rate was shown for those who consistently slept fewer than 5 hours on all nights (HR, 1.65; 95% CI, 1.22 - 2.23) compared with those who consistently slept 6 to 7 hours per night; and there was a 25% higher mortality rate for those who averaged 8 hours or more of sleep on all nights (HR, 1.25; 95% CI, 1.05 - 1.50).
As mentioned, no significant associations were found in the participants aged 65 years or older.
The suggestion that sleeping more hours over the weekend may compensate for staying up late during the week, at least in the younger age group, appears to diverge from past research, note the investigators. But they point out that this is probably because "previous work has focused on weekday sleep only." Also, the two types of sleep differ over causes, consequences, duration, and effect from age, they add.
Still, the "interpretation of results on sleep duration in terms of sufficient or insufficient recovery or compensatory sleep is speculative," the researchers write.
"It needs confirmation in studies that link changes in sleep duration…in a longitudinal approach across many weeks," they add.
The study was funded by AFA Insurance and the Italian Institute of Stockholm, Sweden. The study authors have disclosed no relevant financial relationships.
J Sleep Res. Published online May 22, 2018. Abstract
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Cite this: Weekend Sleep-in May Lower Mortality Risk - Medscape - May 25, 2018.