Sleep can protect the brain from 83 diseases: how many hours you need to sleep

A large study by Chinese scientists published in the journal PLOS Medicine showed that a longer duration of rapid eye movement (REM) sleep is associated with a lower risk of 83 diseases, including dementia, heart failure and Parkinson's disease. The optimal sleep duration is 6 to 8 hours a day.

A large study by Chinese scientists, published on 17 September in the journal PLOS Medicine, found a link between the duration of certain sleep stages and the risk of developing dozens of diseases. The study was led by Shengzhi Sun of Capital Medical University in China. The researchers analysed data from 95,559 participants in the British UK Biobank database. Each participant wore a movement sensor on the wrist for a week, and on the basis of those recordings a deep learning algorithm determined sleep stages (REM, deep and light sleep), total sleep duration, time awake after falling asleep, and the difference in sleep schedule from night to night. The participants' health was monitored for an average of 8.9 years. A greater amount of REM sleep turned out to be associated with a lower risk of 83 diseases. With a difference of 47.6 minutes of REM sleep per night, the risk of heart failure was 26% lower, of dementia 46% lower, and of Parkinson's disease 80% lower. More deep sleep was linked to a lower risk of seven diseases, including type 2 diabetes and major depressive disorder. The fewest diseases were noted in those who sleep 6 to 8 hours a day. Those who slept less than five hours fared worst: they have a higher risk of 37 diseases. Irregular sleep and waking up in the middle of the night were linked to a higher risk of anxiety disorders and substance use disorders. The authors of the study emphasise that keeping sleep within 6–8 hours can effectively reduce the risk of many diseases. The study is observational and does not prove a direct causal influence of sleep characteristics on disease risk.