Study: REM sleep linked to lower risk for dozens of diseases

A study published in the journal PLOS Medicine shows that it is not only the number of hours we sleep that matters, but also how sleep is structured throughout the night — and this appears to be linked to the risk of developing numerous health conditions.

The research was carried out by a team led by specialists from Capital Medical University in China, based on data from 95,559 participants in a large-scale research project in the United Kingdom. For approximately one week, participants wore wrist devices that allowed their sleep patterns to be analysed. The data were then correlated with their health status, monitored over a median period of nearly nine years.

REM sleep associated with lower risk for 83 conditions

Particular attention was paid to REM sleep — the stage in which most dreaming occurs and in which brain activity resembles, in certain respects, that of the waking state.

The results show that a greater proportion of REM sleep was associated with a lower risk for 83 of the conditions analysed, including heart failure, Alzheimer's disease, hypotension, and atrial fibrillation. In total, the researchers identified associations between sleep characteristics and 156 different diseases.

Deep sleep was likewise linked to a lower risk for seven conditions, including type 2 diabetes and Parkinson's disease.

The study's authors note, however, that these findings show only statistical associations and do not prove that a particular sleep pattern directly prevents the conditions in question.

Insufficient sleep linked to increased risk for 37 conditions

Sleep duration was another factor examined. People who slept between six and eight hours per night fell within the range associated with the lowest risk for a significant number of diseases.

By contrast, those who slept fewer than five hours per night had a higher risk for 37 conditions, compared with people who slept between six and eight hours.

The researchers also separately analysed the proportion of REM sleep relative to total sleep time, specifically to determine whether the association observed with certain diseases was simply due to some individuals sleeping more hours overall.

Sleep regularity also matters

In addition to sleep duration and the proportions of REM and deep sleep, the researchers tracked how regular participants' sleep was, as well as the time spent awake after initially falling asleep.

Greater sleep irregularity was associated with an increased risk for three diseases, whilst longer periods spent awake after falling asleep were linked to a higher risk for six conditions.

The researchers conclude that sleep health cannot be reduced to the number of hours slept — the way in which sleep stages follow one another, as well as the regularity of sleep, also matter.

Further research is needed

The study's authors emphasise that the biological mechanisms underlying these associations are not yet fully understood and that further research is required. One hypothesis is that REM sleep may influence biological processes distinct from those related to total sleep duration, which would explain why different components of sleep appear to be associated with different categories of disease.

The researchers caution that sufficient and regular sleep, with normal periods of REM and deep sleep, remains an important element of a healthy lifestyle. The study's findings should not, however, be interpreted as evidence that modifying a single component of sleep could, on its own, prevent certain diseases.