Sleeping less than five hours a night was associated with a higher risk of dozens of diseases in a large study that tracked nearly 100,000 adults for almost nine years. The analysis also found that people who spent more time in REM and deep sleep tended to have lower risks of several major conditions, suggesting that both sleep duration and sleep structure may be linked to long-term health.

Researchers analyzed 95,559 UK Biobank participants who wore wrist accelerometers continuously for seven days and nights. A deep learning algorithm estimated total sleep time, REM sleep, deep sleep, light sleep, wakefulness after sleep onset, and how much sleep patterns varied from night to night.

More REM Sleep Was Linked to Lower Disease Risk
Greater REM sleep was associated with lower rates of 83 diseases. Each additional 47.6 minutes of REM sleep was linked to a 26 percent lower rate of heart failure, a 46 percent lower rate of dementia, and an 80 percent lower rate of Parkinson’s disease during follow-up.

More deep sleep was associated with reduced risk of seven conditions, including type 2 diabetes and major depressive disorder. By contrast, greater night-to-night sleep irregularity and more wakefulness after falling asleep were associated with higher risks of several conditions, including anxiety and substance use disorders.

The study did not prove that these sleep patterns directly cause or prevent disease. Because the research was observational, other health, behavioral, or biological factors could contribute to the associations.

A Six to Eight Hour Window Stood Out
Total sleep time showed a nonlinear relationship with many health outcomes. For most of the conditions showing this pattern, the lowest risk was concentrated between six and eight hours of sleep per night.

People who slept less than five hours had the greatest overall vulnerability, with higher risks of 37 conditions. Across the full analysis, researchers identified 156 statistically significant associations between sleep patterns and newly diagnosed diseases after correcting for the large number of comparisons...