Scientists examined more than 43,000 adults for the self-reported study, which was published Wednesday in the Journal of Sleep Research, and followed them for a span of 13 years.
Between 1997 and 2010, 3,234 died. That’s a rate of about six deaths per 1,000 people per year. By 2010, the world mortality rate was about eight in 1,000.
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The adults in the study were grouped by sleep duration. Short sleepers slept for less than five hours per night. Medium sleepers, about seven hours. Long sleepers slept for nine or more hours per night.
The groups were again divided and paired by weekday and weekend sleep habits.
Short sleepers under age 65 who snoozed for an average of five hours or fewer during the week and then slept for at least eight hours on the weekend didn’t have an increased risk of death compared to the adults who slept six to seven hours per night, researchers found.
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But without making up for lost sleep during the week, those only getting five hours of fewer during the week didn’t live as long as people who consistently slept seven hours each night.
Weekend snoozers, the data showed, lives just as long as those who slept enough during the week.
“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 researchers wrote in the study. “This suggests that short weekday sleep may be compensated for during the weekend, and that this has implications for mortality.”
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The researchers also found that people who slept for eight hours or more every day had a 25 percent higher mortality rate compared to those who managed six or seven hours a night.
But the data doesn't show that short or long sleep is somehow responsible for higher mortality, lead author Torbjorn Akerstedt told the Washington Post.
The American Academy of Sleep Medicine and Sleep Research Society recommends adults ages 18 to 60 sleep about seven hours per night.
"Sleeping less than 7 hours per night on a regular basis is associated with adverse health outcomes," the academy wrote in a consensus statement.
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Self-reporting may be considered a limitation of the study, but researchers note it’s a practical way to accumulate large-scale data. They did account for other factors influencing sleep, such as alcohol and coffee consumption, smoking habits, shift work and more.
"The only thing that we don't have control over is latent disease," Akerstedt told the Post. Latent diseases go undetected.
Read the full study at online.library.wiley.com.