We're all prone to a long lie-in on the weekends, especially when we've spent the week getting crummy sleep.

That's a habit which could turn out to be beneficial. According to a study by Swedish and U.S. researchers, people under the age of 65 who get less than five hours sleep on the weekend had an increased risk of death.

The study, published in the Journal of Sleep Research, was based on data from more than 30,000 subjects followed over a 13-year period.

Why a longer snooze on the weekend might be better

For those who only manage to get less than five hours of shut eye throughout the week, but then have a longer snooze on the weekends, there was no heightened mortality risk.

There is a higher mortality risk if a person is consistently getting short (less than five hours) or long (more than nine hours) sleep, compared to people who are consistently sleeping around six to seven hours sleep throughout the week.

Researchers came to those findings after taking into account factors which affect mortality, such as gender, education, body mass index, severe disease, use of hypnotics (like sleeping pills), plus aspects like smoking, alcohol intake, physical activity, coffee intake, and employment status.

Torbjörn Åkerstedt, a clinical neuroscience professor at Sweden's Karolinska Institute and one of the authors of the paper, said the findings are consistent with previous research into sleep duration's link to mortality.

However, these previous studies focused on weekday sleep, and Åkerstedt said the team "suspected that may not be enough." The investigation into weekend sleep suggests that getting a long one could help prevent an early death.

"The results imply that short (weekday) sleep is not a risk factor for mortality if it is combined with a medium or long weekend sleep," the authors of the paper wrote.

"This suggests that short weekday sleep may be compensated for during the weekend, and that this has implications for mortality."

But maybe don't fret if you're over 65

For people over the age of 65, no link between sleep duration and a heightened risk of death was established. Åkerstedt said it's probably because older people "get the sleep they need."

"They sleep as much during weekdays as during weekends whereas the difference is huge in lower age groups," he explained.

"We also note that the the older participants are 'well rested' when they wake up, whereas the younger are definitely not 'well rested.' Our interpretation is that sleep need is reduced with increasing age."

There were limitations to the study, such as the participants only being asked about their sleeping habits only once, making it impossible to detect changes in their sleep habits over time.

"We would have had stronger results if we had collected sleep duration reports every 5 years, for example," Åkerstedt added.

"People change their sleep duration over time. Thus, our results may contain an underestimation of risk."

（作者：汽车音响）