According to the researchers, this means that people who were impaired from chronic sleep restriction were unaware of any impairment.
The research found that individuals who managed just a few hours' sleep each day during the week but then had a long snooze at weekends had no raised mortality risk, compared with those who consistently stuck to six or seven hours a night.
The study followed the sleep habits of 43,880 subjects over the course of 13 years. They are the ones who can compensate with longer rest on the weekends, because there is not as much of a deficit. In the same age group, short sleep (or long sleep) on both weekdays and weekend showed increased mortality. He was not involved in the new study. We can't deposit zzzs over the weekend and expect to cash them out later.
The study has its limitations, as participants were asked to recall their sleep patterns rather than being observed sleeping, but Åkerstedt has an idea about what might be driving this difference in mortality. For the sleep-deprived, sleeping in on a weekend is like eating a salad after a series of hamburger dinners - healthier, sure, but from "one perspective the damage is done". The adults in the study were grouped by sleep duration. People in their late teens and 20s slept on average for seven hours a night during the week but 8.5 hours on days off.
However, people who slept for eight or more hours, seven days a week, were found to have a 25 per cent higher mortality rate compared with those who kept to six or seven hours a day.
Previous studies have found a U?shaped relationship between mortality and (weekday) sleep duration. Torbjörn said it's probably because older people "get the sleep they need".
Grandner urged the overworked and underslept not to view sleep as time lost.