New research indicates that higher amounts of rapid eye movement (REM) sleep are associated with significantly lower risks of various diseases, including dementia, Parkinson’s disease, and heart failure. This study examined 95,559 adults who wore wrist accelerometers continuously for seven days and nights. Researchers from China employed deep-learning algorithms to analyze different sleep stages and subsequently evaluated health records over nearly nine years.

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The findings revealed that greater REM sleep correlated with an 80% lower risk of Parkinson’s, a 46% lower risk of dementia, and a 26% lower risk of heart failure. Additionally, increased deep sleep was related to decreased risks of seven conditions, including Type 2 diabetes and major depressive disorder.

Sleep duration also played a crucial role. The study identified that six to eight hours of sleep per night was associated with the lowest risk for 69 diseases. Conversely, sleeping fewer than five hours was linked to an increased risk of 37 health conditions. Researchers noted that greater night-to-night sleep irregularity and increased wakefulness during the night were connected to higher risks of anxiety and substance use disorders.

These results were published on September 17 in PLOS Medicine. Dr. Oki Ishikawa, a sleep medicine expert, emphasized the importance of both total sleep duration and the percentage of REM sleep. Average REM sleep in the study group was about 20%, falling within the normal range of 20-25% per sleep cycle.

Dr. Chelsie Rohrscheib, head sleep expert at Wesper, noted that disrupted sleep could be an early warning sign of diseases like Parkinson's and heart failure, which may begin to affect sleep years before diagnosis. Both experts acknowledged limitations in the study, such as its observational nature, which cannot definitively prove causation and the reliance on wrist devices, which may not fully capture sleep stages compared to clinical sleep studies.

Researchers highlighted that while changes in sleep could hint at underlying health issues, the study doesn’t conclusively determine whether poor sleep is a cause of diseases or an early symptom. They called for further research to investigate the potential for increasing REM or deep sleep to help prevent disease.