A recent study conducted by researchers at Capital Medical University in Beijing analyzed sleep patterns among 95,559 participants from the UK Biobank, investigating the relationship between various sleep stages and health risks. The findings reveal that increased rapid eye movement (REM) sleep is associated with a lower risk of 83 health conditions in middle-aged and older adults, while insufficient sleep—defined as less than five hours—correlates with higher disease risks.
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Participants used accelerometers on their wrists for a week to track their sleep. A specialized program, SleepNet, classified their sleep into stages and provided insights into total sleep duration, wakefulness after falling asleep, and night-to-night sleep variability. The researchers tracked health outcomes over a median period of 8.9 years, identifying notable health implications related to different sleep stages.
Those who averaged over 82 minutes of REM sleep per night exhibited a significantly lower risk for various conditions, including a 25% reduced risk of heart failure and a 46% lower risk of dementias. In contrast, deep sleep was only linked to seven conditions, including type 2 diabetes and Parkinson’s disease, indicating that the benefits of REM sleep are more extensive.
The analysis suggested that for the 86 conditions examined, the optimal total sleep duration falls within the 6 to 8-hour range. Individuals sleeping less than five hours accounted for 37 of the 41 increased risk associations found in the study. Dementias were about 2.6 times more common, primary Parkinson's disease was 2.4 times more prevalent, and heart failure risk was 1.7 times greater among the shortest sleepers.
However, those who sleep for more than eight hours also face increased risks of major depressive disorder, suggesting a complicated relationship between sleep duration and mental health. The researchers indicated that oversleeping could be a symptom rather than solely a cause of depression.
Moreover, the study noted that inconsistency in sleep patterns could contribute to health issues, with irregular sleep habits linked to anxiety disorders and abdominal pain. The quality of sleep, as reflected by time spent awake after initially falling asleep, was associated with ailments like alcohol abuse and osteoarthritis.
While the findings highlight critical sleep stage disparities, the researchers acknowledged limitations in their methodology. The wrist-based tracking system underreported REM sleep by about 17 minutes and overestimated non-REM sleep stages. Furthermore, data from the study may not represent the general population due to the Biobank's participant demographics, which skewed towards healthier and predominantly white individuals.
Despite the association between sleep patterns and health risks, the study does not establish causality. The authors emphasize the need for further studies to explore direct effects, particularly through controlled trials involving modifications to sleep patterns. The full study has been published in the journal PLOS Medicine.