We all suffer from too little sleep. Maybe you stayed up until 3:00 A.M. swiping on Tinder or trained all night for a Fortnite tournament, and now you’re feeling sluggish at work, yawning up a storm. Fortunately, say researchers in a new Journal of Sleep Research study, you’re not going to be in dangerous sleep debt forever.
In the paper, published Wednesday, an international team of neuroscientists and epidemiologists present good news and bad news. The bad news is that sleeping too little can increase a person’s risk of dying early. The good news is really good for people who try to catch up: Sleeping for longer on the weekend, they write, seems to cancel out that risk. The authors, led by Stockholm Stress Center director Torbjörn Åkerstedt, Ph.D. came to this conclusion by analyzing the relationship between weekday sleep, weekend sleep, and mortality data collected from 43,880 people over 13 years. Among their many findings, they showed that people who slept five hours or less on weekdays and either medium (seven hours) or long (nine hours) amounts of time on weekends had no significant change in their mortality rates compared to people who didn’t sleep in on the weekends. This is an important observation, considering how seriously mortality risk changes as a result of poor sleeping.
The team found that people under 65 years old who slept less than five hours a night on weekends had a 52 percent higher chance of dying during the 13-year study period; as people got older, this effect became less profound. In addition, people under 65 who slept less than five hours on weekends and weekdays appeared to have a 65 percent higher mortality rate than people who slept seven hours a night. Notably, they also found a 25 percent higher mortality risk for people who consistently slept more than nine hours a night.
In short, the evidence suggests what we’ve always known: It’s important to get as much sleep as you can, whenever you can. You may still feel groggy on weekdays if you wait until the weekend to catch up on your sleep, but the research suggests that you won’t shorten your life because of it. The study’s authors are careful to note, though, that this “catching up” interpretation is speculative and has not yet been verified in experiments.
“This interpretation … needs confirmation in studies that link changes in sleep duration between weekend and weekday in a longitudinal approach across many weeks,” they write. “This would tell us if weekday sleep reduction is linked to weekend sleep extensions and, ideally, the data would be able to extend our conclusion if linked to subsequent mortality.”
So while future studies will be required to know for sure whether the effect observed in this study is indeed one of weekend recovery from insufficient weekday sleeping, suffice it to say that you should really just try to get at least seven hours a night. But if you can’t or don’t, at least make sure to sleep in on your days off work. Your body will thank you.