Spending more time in REM sleep is associated with a lower risk of developing a wide range of diseases in the following years. This is reported by a research team from Capital Medical University in Beijing in the journal PLOS Medicine. The analysis was based on data from 95,559 people in the UK Biobank.

How the study was conducted

Participants wore a wrist-worn activity sensor for seven days and nights. Using machine learning, researchers estimated sleep stages: REM sleep, deep sleep, and light sleep, as well as total sleep duration, nighttime awakenings, and sleep regularity. The researchers then tracked which of over 1,000 diseases appeared in participants’ health records over an average period of 8.9 years.

Key findings

  • REM sleep: More REM sleep was linked to a lower risk for 83 diseases, including heart failure (risk about a quarter lower), dementia (about half as high), and Parkinson’s disease (significantly lower). The comparison was between people whose REM sleep differed by about 48 minutes per night.
  • Deep sleep: More deep sleep was associated with a lower risk for seven diseases, including type 2 diabetes and depression.
  • Sleep duration: The lowest disease risk was seen with six to eight hours of sleep. Those sleeping less than five hours had an increased risk for 37 diseases.
  • Restless sleep: Irregular sleep schedules and frequent nighttime awakenings were linked to a higher risk of anxiety disorders and addiction.

What the study does not show

This is an observational study. It shows associations, but does not prove that sleep prevents disease. The authors acknowledge this themselves. The reverse is also possible: a disease that develops unnoticed over years may alter sleep patterns early on. For example, REM sleep disturbances are known as an early warning sign of Parkinson’s disease.

Additionally, a wrist sensor can only estimate sleep stages. Accurate measurement requires a sleep lab and brainwave monitoring. And only a single week was measured, which may not represent years of sleep patterns.

What you can take away from this

The findings are in line with longstanding sleep research recommendations: get enough sleep—ideally six to eight hours—and keep a regular schedule. REM sleep cannot be “switched on” at will. It mainly occurs in the second half of the night, so you get more of it if you don’t have to get up too early or aren’t jolted awake by an alarm. Alcohol in the evening is known to suppress REM sleep.

If you consistently sleep poorly, don’t brush it off as a minor issue—talk to your primary care provider about it.

The video

Our short video explains why too much sleep can leave you just as tired as too little:

As Ibn Sina wrote about a thousand years ago:
النوم المعتدل ممكّن للقوة الطبيعية من أفعالها، مريح للقوة النفسانية
“Moderate sleep enables the natural force to do its work and gives the soul’s force rest.”
Canon of Medicine, Book I, Art 3, Chapter on Sleep and Wakefulness; from the Arabic.

Source: Luo et al., “Accelerometer-derived real-world sleep stages and risk of incident diseases: A UK Biobank cohort study and phenome-wide association analysis,” PLOS Medicine, September 17, 2026, doi:10.1371/journal.pmed.1005213.