How much sleep do you actually need? A new study has the answer

We all know sleep matters, but a new study published September 17th in PLOS Medicine, first covered by EurekAlert, puts an actual number on just how much, and the results are eye-opening. 

Researchers led by Shengzhi Sun of Capital Medical University tracked 95,559 people from the UK Biobank, who wore wrist accelerometers for a full week. From that data, a deep-learning algorithm broke down each person’s sleep into stages, tracked how long they slept, how much they tossed and turned after waking up mid-sleep, and how much their schedule shifted from one night to the next. 

The team then followed everyone for close to 9 years and checked their health records against more than 1,000 diseases.

What happens if you get more REM sleep?

Turns out, REM sleep is doing a lot of heavy lifting for your health. People who got more REM sleep had a lower risk of 83 different diseases, including a 26% lower risk of heart failure, a 46% lower risk of dementia, and an 80% lower risk of Parkinson’s disease. Deep sleep helped too, though with a shorter list of 7 conditions, including type 2 diabetes and major depressive disorder.

On the flip side, an irregular sleep schedule and more time spent lying awake after falling asleep were both linked to a higher risk of conditions like anxiety and substance use disorders.

Why does the 6 to 8 hour window matter so much?

The study found that more sleep isn’t always better. Instead, the sweet spot sits between 6 and 8 hours a night, and that’s where researchers found the lowest disease risk for most of the 86 conditions they studied. Sleep less than 5 hours, though, and your risk climbs fast, with the study linking short sleep to a higher risk of 37 different conditions.

As Sun and his team put it, “Maintaining a sleep duration of 6-8 hours can effectively reduce the risk of multiple diseases, providing new insights for health promotion and preventive practice.”

The researchers note this is an observational study, so it can’t prove bad sleep directly causes disease. But the pattern is hard to ignore. If you’ve been skimping on sleep to squeeze more into your day, this might be the nudge you need to rethink that trade-off.