Getting enough sleep is often linked to better energy, mood and concentration. However, a new study says that what happens during sleep may matter as much as how long we sleep. A large study has found that people who spent more time in rapid eye movement (REM) sleep had a lower risk of developing several diseases, including dementia and heart failure. The findings, published in PLOS Medicine, come from an analysis of sleep and health data from more than 95,000 people and add to growing evidence.

REM sleep is one of the stages of the sleep cycle and is associated with dreaming, memory processing and emotional regulation. In the new study, higher amounts of REM sleep was linked to a lower risk of 83 diseases. The researchers also found that sleeping around six to eight hours was linked with the lowest risk for many health conditions. However, the study does not prove that getting more REM sleep directly prevents dementia, heart disease or other illnesses.

What Did The Study Find?

Researchers from China analysed data from 95,559 UK Biobank participants who wore wrist accelerometers for seven consecutive days and nights. Using a deep-learning algorithm, researchers estimated different sleep stages, including REM and deep sleep, as well as total sleep duration, sleep irregularity and the amount of time people remained awake after falling asleep. Participants were followed for a median of 8.9 years. The researchers then examined the relationship between sleep patterns and 1,049 health outcomes.

The study found that a higher amount of REM sleep was associated with a lower risk of 83 diseases. The association included dementia, heart failure and Parkinson's disease. An increase in REM sleep equivalent to the study's interquartile range of 47.6 minutes was associated with a hazard ratio of 0.54 for dementia and 0.74 for heart failure.

How Can REM Sleep Affect Health?

REM sleep is an active stage of sleep during which brain activity increases. It plays a role in processes related to memory and emotional processing.

The findings suggest that having a healthier distribution of sleep stages may be associated with better long-term health. However, the study was designed to identify associations rather than establish exactly how REM sleep might impact individual diseases. This is important because factors such as age, lifestyle, existing health problems and other aspects of sleep can also influence disease risk.

Sleep And Dementia

In this study, greater REM sleep was associated with a lower risk of dementia. One possible explanation is that healthy sleep patterns support processes involved in brain maintenance and memory. But this research cannot establish that increasing REM sleep in someone who currently gets less REM would prevent dementia.

Sleep And Heart Disease

The study also found an association between greater REM sleep and lower risk of heart failure. This suggests that sleep architecture may be linked with cardiovascular health, beyond simply counting the number of hours spent in bed. Poor or disrupted sleep can happen along with several factors that affect cardiovascular health. The study also found that higher wakefulness after falling asleep was associated with higher risks of several diseases. This highlighted the importance of uninterrupted sleep.

How Many Hours Of Sleep Are Linked To Lower Risk?

The researchers found that sleep duration had a non-linear relationship with the risk of many diseases. For 69 health conditions, the duration associated with the lowest risk was concentrated in the six-to-eight-hour range.

Very short sleep stood out as a concern. People sleeping for less than five hours had the most adverse associations, accounting for 37 of 41 significant associations when compared with the six-to-eight-hour reference group.

This does not mean that six hours of sleep is an ideal target for everyone. Individual sleep needs can vary, and the study did not test whether changing sleep duration would directly prevent disease.

Should You Try To Increase REM Sleep?

Rather than trying to control REM sleep alone, the findings support paying attention to overall sleep health. Maintaining a regular sleep schedule, allowing enough time for sleep and addressing repeated nighttime awakenings may help improve sleep patterns.

The new study suggests that more REM sleep is associated with a lower risk of dementia, heart failure and many other diseases. It also highlights a six-to-eight-hour sleep window that was associated with lower risk for many conditions. However, the research is observational, and it cannot establish cause and effect.

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