A good night’s sleep can protect health in more ways than just making people feel refreshed.
One large study found that people who spent more time in REM sleep and deep sleep tended to have a lower risk of many diseases – while very short sleep was linked to poorer health.
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The research was led by Shengzhi Sun of Capital Medical University in China and colleagues. It was published Sept. 17 in the openly available journal PLOS Medicine.
The researchers analyzed data from 95,559 people in the UK Biobank. Participants wore wrist devices continuously for seven days, which allowed the researchers to estimate how long they slept, and how their sleep changed during the night.
The team examined REM sleep, deep sleep, and light sleep, as well as total sleep time. They also measured how often people woke up after falling asleep, and how much their sleep patterns varied from night to night.
The participants were then followed for an average of almost nine years. The researchers compared their sleep patterns with medical records covering over 1000 health conditions.
More REM sleep was associated with a lower risk of 83 diseases. Among these were heart failure, dementia and Parkinson’s disease.
REM sleep is the phase in which vivid dreams often occur, and in which the brain is highly active. It is thought to play important roles in memory, learning, and emotional processing.
More deep sleep was linked to a lower risk of seven conditions, including type 2 diabetes and major depression. Deep sleep is a particularly restorative phase in which the body performs important repair and recovery processes.
Sleep duration was also important. For many conditions, the lowest risk was seen among people who slept about six to eight hours per night, while those who slept less than five hours had an increased risk of 37 conditions.
Having an irregular sleep pattern or spending more time awake after first falling asleep was also associated with a higher risk of several conditions. Among these were anxiety and substance use.
The findings are particularly relevant because poor and irregular sleep is common. The researchers noted that China’s “2026 Sleep Health White Paper” found an average reported sleep time of 6.97 hours, while 23 percent of respondents slept less than six hours.
The study is strong because it used wearable devices instead of relying on people’s own memories of their sleep, and followed a very large group for years. However, the wrist devices estimated sleep stages rather than measuring brain activity in a sleep lab.
Most importantly: This was an observational study. It can’t prove that more REM or deep sleep prevents disease, and existing health problems can themselves affect sleep.
Still, the results add evidence that sleep duration, quality, and regularity can all have an impact on long-term health. They also suggest that simply looking at the total number of hours you sleep can overlook important information about how well you actually sleep.
Source: Capital Medical University.
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