Prolonged REM sleep lowers risk of Parkinson’s and dementia

Prolonged time spent in REM sleep significantly lowers the risk of developing 83 chronic health conditions, including Parkinson’s disease and dementia, according to an international study published in September 2026.

Sleep Duration and Chronic Disease Risk

The team analyzed one week of sleep stages—including REM, deep, and light sleep—recorded by wrist-mounted sensors and processed using artificial intelligence algorithms. By tracking participants’ health records over an average of nine years, the investigators mapped the associations between specific sleep patterns and numerous different diseases.

Specific Disease Reductions Linked to REM Sleep

The analysis revealed that every 47-minute increase in REM sleep duration provides substantial protection against 83 distinct medical conditions. Individuals who achieved sufficient REM sleep experienced an 80 percent reduction in Parkinson’s disease risk, a 46 percent drop in dementia risk, and a 26 percent decrease in heart failure risk.

The study also identified crucial benefits associated with the deep sleep phase. Participants who regularly obtained adequate deep sleep showed significantly lower risks of type 2 diabetes and major depressive disorder. Conversely, frequent nighttime awakenings and irregular sleep schedules were found to trigger higher risks of anxiety disorders.

General Sleep Guidelines and Vulnerable Groups

Investigators emphasized that the optimal nightly sleep duration ranges between six and eight hours. Adults who sleep less than five hours per night represent the most vulnerable demographic, facing a sharply elevated risk of developing 37 different illnesses. Study authors noted that maintaining a consistent six-to-eight-hour sleep schedule serves as a vital preventive healthcare measure for both adults and older individuals.