Researchers analyzing nearly 95,000 adults discovered that getting more REM sleep, the stage where most dreaming occurs, was associated with a significantly lower risk of 83 different diseases. The finding, published in PLoS Medicine in September 2026, suggests that the type of sleep you're getting each night may be just as important as how many hours you're sleeping.

Which Sleep Stage Matters Most for Disease Prevention?

The study, conducted by researchers from Peking University and Capital Medical University in Beijing, analyzed data from participants who wore wrist accelerometers for a week to track their sleep patterns. Researchers then followed these participants for a median of 8.9 years, comparing their sleep characteristics with 1,049 different health outcomes.

REM sleep, or rapid eye movement sleep, is the stage where your eyes move rapidly beneath closed eyelids and vivid dreaming typically occurs. During this stage, your brain is actively working to support cognitive functions, emotional regulation, brain development, and memory consolidation. The research found that increased REM sleep duration was associated with lower risk of dozens of serious conditions, including:

• Cardiovascular conditions: Heart failure, hypotension (low blood pressure), and atrial fibrillation
• Neurological diseases: Dementia, Alzheimer's disease, Parkinson's disease, and parkinsonism (a group of brain conditions causing slowed movements and tremors)
• Autoimmune and other conditions: Multiple sclerosis and various other health outcomes across 12 disease categories

Deep sleep, the most physically restorative stage when brain activity slows significantly, showed a different pattern. Increased deep sleep duration was associated with lower risk of seven specific conditions, including type 2 diabetes, major depressive disorder, sleep apnea, and Parkinson's disease.

What's the Ideal Sleep Duration and Pattern?

The researchers found that people who slept between six to eight hours per night had the best overall sleep patterns and the lowest risks for various diseases. This finding differs slightly from the familiar seven-to-nine-hour recommendation many people have heard, but experts emphasize that sleep needs vary from person to person.

Notably, the six-to-eight-hour group had the highest proportion of REM sleep and the least disruption during deep sleep. They also experienced fewer nighttime awakenings and more consistent sleep from night to night. People getting less than five hours of sleep had 37 of the 41 significant health risks identified in the analysis when compared with the six-to-eight-hour group, including heart failure, type 2 diabetes, and chronic obstructive pulmonary disease (COPD, a lung condition).

Sleeping more than eight hours was linked to fewer health risks overall, although it was associated with a higher risk of major depressive disorder.

How to Improve Your Sleep Quality and Consistency

While the study identifies important associations between sleep patterns and disease risk, experts stress that the goal isn't perfection but rather creating a sustainable sleep routine. Here are practical steps supported by the research:

• Keep a consistent schedule: Try to go to bed and wake up around the same time each day, including on weekends. Sleep regularity matters; people whose sleep duration changed significantly from night to night had higher risks of anxiety and major depressive disorder.
• Protect your sleep window: Give yourself enough time to get the amount of sleep your body needs rather than routinely squeezing sleep into the leftovers of your day. Aim for a window that allows six to eight hours of sleep.
• Address common disruptors: Late-day caffeine, alcohol, stress, and screens before bed can all interfere with sleep quality and the time you spend in restorative sleep stages.
• Watch for persistent sleep problems: Frequent waking, loud snoring, or feeling exhausted despite spending enough time in bed can be signs of sleep disorders like sleep apnea or insomnia. If these issues occur regularly, talk with a health professional.

Why Sleep Is Emerging as a Pillar of Health

Sleep researchers are increasingly recognizing sleep as equally important to diet and exercise for healthy aging. For more than two decades, sleep researcher Dr. Katie Stone at the Sutter Health Research Institute has helped advance understanding of how sleep affects dementia, heart health, falls, fractures, and overall aging.

"Sleep is crucial for physical and mental health and for regulating physiological and behavioral processes, so it is not surprising that poor sleep is associated with the development of so many diseases," said Nour Makarem, co-director of the Chronic Disease Unit at Columbia University.

Nour Makarem, Co-director of the Chronic Disease Unit, Columbia University

During sleep, particularly deep sleep, the brain's glymphatic system removes metabolic waste and toxins that accumulate during waking hours. This housekeeping function is thought to be critical for preventing neurodegenerative diseases like Alzheimer's and dementia. Poor sleep is also linked to hormonal imbalances, weight gain, increased stress and inflammation, and disruption of the body's circadian rhythms, all of which can predispose people to chronic disease.

"Sleep is not just a reflection of health. It may actively influence how the brain and body age over time," noted Dr. Katie Stone, a sleep researcher at Sutter Health Research Institute.

Dr. Katie Stone, Sleep Researcher, Sutter Health Research Institute

What Are the Study's Limitations?

Experts note important caveats to the findings. Sleep stages were estimated from wrist accelerometry rather than measured directly with polysomnography, which is considered the gold standard in sleep medicine. While wearable devices are useful for tracking sleep in large populations, they don't provide the same physiological precision as laboratory sleep studies.

Additionally, the study shows associations between sleep patterns and disease risk, not proof that changing a specific sleep stage will prevent disease. Some of the links could reflect "reverse causation," meaning that symptoms of a condition result in changes to sleep patterns rather than the other way around. For example, depression itself disrupts sleep, so the association between light sleep and depression may work both directions.

Researchers emphasize that the next steps include replicating these findings in more diverse populations and determining which sleep features are causal pathways to disease versus early markers of disease development.