More REM sleep linked to lower risk of 83 diseases in study of 95,000 people

People who get more REM sleep — the stage associated with vivid dreaming — face meaningfully lower odds of developing 83 diseases, including dementia, heart failure, and Parkinson's disease, according to a large study published September 17 in the journal PLOS Medicine. The finding comes from nearly nine years of health records on more than 95,000 adults whose sleep was tracked not by asking them how long they slept, but by wrist-worn sensors that recorded their actual sleep stages night after night.

The scale and method set this study apart from most prior sleep research. Researchers led by Shengzhi Sun of Capital Medical University, China, and colleagues analyzed accelerometer data from 95,559 UK Biobank participants, using a deep-learning algorithm called SleepNet to derive REM, light, and deep sleep stages, total sleep duration, night-to-night irregularity, and wakefulness after sleep onset. Participants were followed for a median of 8.9 years, with health records tested against more than 1,000 disease outcomes.

The headline result: for every interquartile range increase in REM sleep — roughly 47.6 minutes — the risk of 83 conditions was lower. The associations were especially pronounced for neurological diseases. People with greater REM sleep had a hazard ratio of 0.54 for dementia, meaning roughly half the risk compared to those with less REM, and a hazard ratio of just 0.20 for Parkinson's disease. Heart failure showed a hazard ratio of 0.74.

Deep sleep — also called slow-wave sleep — showed a narrower but still meaningful benefit, linked to lower risk of seven conditions including type 2 diabetes and major depressive disorder. Light sleep, by contrast, was associated with higher risk of some conditions such as major depressive disorder, though it showed lower risk for others including heart failure and cellulitis, a pattern the researchers did not fully explain.

Sleep fragmentation mattered too. Greater sleep irregularity and higher wakefulness after sleep onset — the total time a person is awake after initially falling asleep — were each associated with elevated risk of several conditions, including anxiety and substance use disorders. Wakefulness after sleep onset was linked to increased risk of six conditions in total.

Total sleep duration followed a non-linear pattern. For 86 disease categories, risk was not simply lower with more sleep or higher with less — it curved. The lowest risk for 69 of those conditions fell within a 6-to-8-hour window. People sleeping fewer than five hours faced the sharpest increase in vulnerability, with elevated risk across 37 conditions. A longer overall sleep duration was associated with lower risk of at least 50 conditions.

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, likely attributable to more favorable distributions of sleep stages. Maintaining a sleep duration of 6-8 hours can effectively reduce the risk of multiple diseases, providing new insights for health promotion and preventive practice.— Luo J, Liu R, Yin J, Cao W, Sun S, Chen R, study authors

Across all sleep metrics combined, the phenome-wide association analysis identified 156 significant associations between sleep patterns and incident diseases after applying Bonferroni correction — a statistical threshold designed to reduce false positives when testing many outcomes at once.

A critical caveat runs through the findings: because this is an observational study, it cannot establish that sleep patterns directly cause disease. The authors specifically flag the problem of reverse causation — the possibility that early, undetected disease disrupts sleep rather than disrupted sleep causing disease. Depression is a clear example: disturbed sleep is a known symptom of depression, so the association between poor sleep and depression risk may partly reflect illness already underway at the time of measurement.

The study's use of wrist accelerometers rather than polysomnography — the clinical gold standard for measuring sleep stages, which requires electrodes and a sleep lab — is both a strength and a limitation. Accelerometers made it possible to collect real-world data from nearly 100,000 people over a week of normal life, something polysomnography cannot do at scale. But wrist movement is an indirect proxy for brain activity, and the deep-learning algorithm's classifications carry their own margin of error.

For readers who struggle with sleep quality, experts not involved in the study offered practical guidance when contacted by Medical News Today. Scott Nass, MD, a board-certified family medicine physician, recommended maintaining a consistent wake-up time every day including weekends, noting that sleeping in after a poor night shifts the sleep pattern and makes the following night harder. He also suggested that morning daylight shortly after rising helps reinforce the body's sleep-wake rhythm.

Repeatedly going to bed awake and anxious about sleeping can make the brain associate the bed with frustration and alertness.— Scott Nass, MD, board-certified family medicine physician, SwiftCareMD

Chelsie Rohrscheib, PhD, head sleep expert and neuroscientist at Wesper, emphasized keeping the bedroom quiet, dark, and cool — between 65 and 70 degrees Fahrenheit — because the body's core temperature must drop to initiate and sustain sleep. She also recommended a relaxing pre-bedtime routine for at least 30 to 60 minutes before sleep, such as light reading, a warm bath, or listening to calming music.

Why it matters — This is among the largest objective studies of sleep stages and disease risk ever conducted, and its findings suggest that the quality and composition of sleep — not just its duration — may be a meaningful, potentially modifiable factor in the risk of dozens of serious conditions.

Reported by sciencedaily.com, journals.plos.org, eurekalert.org, medicalnewstoday.com, sciencealert.com