By Deborah Brauser
WebMD Health News
A study of nearly 40,000 people showed that for people younger than 65, getting an average of 5 hours or less of sleep per night over the weekend increased the odds of death by 52%, compared with getting at least 7 hours of sleep.
Having short sleep on both the weekdays and weekend, as well as having long sleep at both times, also raised the risk in this age group.
But the death rate among people who got less sleep during week and more sleep on the weekends did not differ a whole lot from those who averaged 7 hours per night.
"Possibly, long weekend sleep may compensate for short weekday sleep," write the investigators, led by Torbjörn Åkerstedt, PhD, of the Karolinska Institute's Department of Clinical Neuroscience in Stockholm, Sweden. But they say more research is needed.
There were no significant links between sleep and risk of death in people 65 or older.
"Previous studies have found a 'U-shaped relationship' between mortality and (weekday) sleep duration," the investigators write. This means "both short and long sleep [was] associated with higher mortality," they add.
But study results have been inconsistent, they say, especially when it comes to measuring weekday or weekend sleep.
In the current study, the researchers studied 43,880 people in the Swedish National March Cohort, all of whom filled out a 36-page questionnaire on lifestyle and medical history. Of those, 38,015 people were followed for 13 years (October 1997 through December 2010).
They were placed into subgroups based on average sleep at the beginning of the study, from "short" (less than 5 hours per night) to "long" (more than 9 hours per night). A reference group received 7 hours of sleep regularly.
There was a 65% higher death rate for people who regularly slept less than 5 hours on all nights, compared with people who regularly slept 6 to 7 hours per night. There was a 25% higher death rate for people who averaged 8 hours or more of sleep on all nights.
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 differ from past research, the investigators say. But they point out that this is probably because "previous work has focused on weekday sleep only."
The study was funded by AFA Insurance and the Italian Institute of Stockholm, Sweden. The study authors have disclosed no relevant financial relationships.