• Rapid eye movement (REM) sleep is necessary for the body to repair itself
• People with lower levels of REM sleep were found to have higher mortality
• We should get the right amount of sleep – seven hours recommended for adults

Deep sleep is essential for good health, and too little of it may shorten your life, a new study suggests.

REM (rapid eye movement) sleep is when dreams occur and the body repairs itself from the ravages of the day. For every 5% reduction in REM sleep, mortality rates increase 13% to 17% among older and middle-aged adults, researchers report.

“Numerous studies have linked insufficient sleep with significant health consequences. Yet, many people ignore the signs of sleep problems or don’t allow enough time to get adequate sleep,” said lead researcher Eileen Leary. She is a senior manager of clinical research at Stanford University in Palo Alto, California.

“In our busy, fast-paced lives, sleep can feel like a time-consuming nuisance. This study found in two independent cohorts that lower levels of REM sleep were associated with higher rates of mortality,” she said.

Ways to optimise REM

How REM sleep is associated with risk of death isn’t known, Leary said. Also, this study couldn’t prove that poor REM causes death, only that it’s associated with an increased risk of dying early.

“The function of REM is still not well understood, but knowing that less REM is linked to higher mortality rates adds a piece to the puzzle,” she said.

It’s still too early to make recommendations about improving REM sleep based on this study, Leary said.

“As we learn more about the relationship, we can begin looking at ways to optimise REM. But that is outside the scope of this project,” she said.

For the study, Leary and her colleagues included more than 2 600 men, average age 76, who were followed for a median of 12 years. They also collected data on nearly 1 400 men and women, average age 52, who were part of another study and were followed for a median of 21 years.

Reliable predictor of mortality

Poor REM sleep was tied to early death from any cause as well as death from cardiovascular and other diseases, the researchers found.

REM sleep’s links to mortality were similar in both groups.

“REM sleep appears to be a reliable predictor of mortality and may have other predictive health values,” Leary said. “Strategies to preserve REM may influence clinical therapies and reduce mortality risk, particularly for adults with less than 15% of REM sleep.”

Previous studies have focused on total sleep time and have shown that both not enough total sleep and too much total sleep can be associated with increased risk of dying early, said Dr Michael Jaffee, an associate professor of neurology at the University of Florida in Gainesville.

“When we sleep, we go through different stages to include REM sleep. REM describes our eye movements during this stage and is also the state associated with when we have dreams,” he said.

This study shows that it is not just total sleep time that may be important, but assuring the right balance of the different stages of sleep, said Jaffee, who co-authored an editorial that accompanied the study.

Proper sleep time

Neurologists need to look for conditions affecting patients, such as obstructive sleep apnoea, that can reduce REM, and doctors should also be aware that certain medications they prescribe can reduce REM, he said.

The study also opens up additional avenues for research to determine if scientists should focus on treatments that affect not just total sleep but target sleep stage balance, Jaffee said.

“This study shows yet another reason for the importance of proper sleep time – recommendations for adults is seven hours – and a good balance of sleep stages by assuring that any possible conditions, such as obstructive sleep apnoea, that can cause a reduction in REM to be evaluated and managed,” he said.

“Anyone with difficulty with sleeping or with loud snoring can benefit from discussing this with their physician,” Jaffee added.

The report was published online on 6 July in JAMA Neurology.

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