Sleep plays an important role in memory, mood and overall health, but researchers are still learning how different sleep patterns may affect the body over time. A study in China followed more than 95,000 adults and examined both how long they slept and how much time they spent in different sleep stages.
The findings linked shorter sleep to higher risk of dozens of diseases, while more REM and deep sleep were associated with a low risk of several conditions.
The study, published Sept. 17, was led by Jingsong Luo of Peking University and examined 95,559 participants from the UK Biobank.
Rather than rely on people to estimate how much they slept, participants wore wrist accelerometers. Small devices worn like watches, they tracked motion continuously for seven days and nights.
Researchers used a deep learning model to estimate total sleep time along with REM, deep and light sleep, periods of wakefulness after falling asleep and how much sleep patterns varied from night to night.
Participants were followed for a median of 8.9 years, with researchers comparing those sleep patterns against health records for more than 1,000 diseases.
The study was observational, so the results show association between sleep and later health outcomes yet cannot prove that sleep patterns directly caused or prevented disease.
The researchers found that several aspects of sleep were associated with later health outcomes. Sleeping less than five hours a night was linked to a higher risk of 37 conditions, while greater amounts of REM sleep were associated with lower rates of 83 diseases.
Each additional 47.6 minutes of REM sleep was linked to a 26% lower rate of heart failure, a 46% lower rate of dementia and an 80% lower rate of Parkinson’s disease during follow-up.
Deeper sleep was also associated with lower risks of seven conditions, including type 2 diabetes and major depressive disorder.
By contrast, greater night-to-night sleep irregularity and more time spent awake after falling asleep were associated with higher risks of several conditions, including anxiety and substance use disorders.
Total sleep time also showed a strong relationship with later health outcomes.
“Sleep duration exhibited significant non-linear associations with 86 disease phenotypes, with the minimum-risk duration for the majority of these conditions (69 phenotypes) precisely concentrated within a 6-8 hour window,” the authors wrote.
In other words, for most of those conditions, the lowest risk was seen among people who slept between six and eight hours a night rather than simply increasing or decreasing with more sleep.
Across the full analysis, researchers identified 156 statistically significant associations between different sleep patterns and newly diagnosed diseases.
The researchers said the findings add to evidence that both sleep duration and sleep stages may be important for long-term health.
“The findings provide additional evidence supporting the role of a 6-8 hours’ sleep duration as a health safeguard for middle-aged and older adults,” the authors wrote.
Overall, the results suggested that sleep health may involve more than simply getting enough hours each night.
The six-to-eight hour range stood out across many conditions, while REM and deep sleep showed separate associations of their own.
The findings offer a broader picture of how different parts of sleep may relate to health over time.
