Full Breakdown
REM and Deep Sleep Linked to Lower Risk of Dementia, Parkinson’s and Other Diseases
By Drooid · · How we work
Study Overview and Key Findings
A large observational analysis of 95,559 adults found that spending more time in rapid eye movement (REM) sleep was associated with substantially lower relative risks of several major conditions. Participants with higher REM sleep had a 46 % lower risk of dementia, an 80 % lower risk of Parkinson’s disease, and a 26 % lower risk of heart failure. Greater deep-sleep duration was linked to reduced risk for seven additional illnesses, including type 2 diabetes and major depressive disorder. The researchers also identified a “sweet spot” of six to eight hours of total sleep per night, which corresponded with the lowest risk for 69 diseases, while sleeping fewer than five hours was tied to higher risk for 37 conditions.
Methodology and Population
The study used wrist-worn accelerometers to record sleep stages continuously for seven days and nights. Deep-learning algorithms parsed the data into REM, deep, light sleep, total duration, wakefulness after sleep onset, and night-to-night irregularity. Health outcomes were drawn from medical records over an almost nine-year follow-up. All participants were drawn from the UK Biobank, a cohort that is generally healthier and less diverse than the broader population.
Expert Interpretation
Oki Ishikawa, M.D., a pulmonary, critical-care and sleep-medicine specialist at Northwell’s Northern Westchester Hospital, emphasized that total sleep duration and the proportion of REM are both important, noting that the average REM share in the sample was about 20 %—the typical range per sleep cycle. Chelsie Rohrscheib, head sleep expert at Wesper, cautioned that the observational design cannot establish causality and highlighted potential measurement limitations of wrist-based devices compared with clinical polysomnography. She also suggested that disrupted sleep may serve as an early indicator of disease, creating a bidirectional relationship between sleep quality and health.
Health Implications
The findings suggest that maintaining adequate REM and deep sleep could be a useful marker for long-term health, though they do not prove that increasing these sleep stages will prevent disease. Associations between sleep irregularity, increased nighttime wakefulness, and higher risks of anxiety, substance-use disorders, and other conditions were also observed.
Practical Recommendations
Both experts advise standard sleep-hygiene practices: keep the bedroom dark, cool and quiet; follow a consistent sleep schedule; limit alcohol and caffeine; and address underlying sleep disorders such as sleep apnea, which can impair REM sleep. Feeling refreshed upon waking and staying alert during the day remain practical gauges of sufficient restorative sleep.