Rapid eye movement (REM) sleep is the fifth stage of sleep and it’s when dreaming occurs. During this stage, your eyes will move rapidly and there’s surge in brain activity, and you will experience higher body temperature, quicker pulse and faster breathing. Now, a new study has shown that people who get less amounts of REM sleep are at greater risks of developing dementia.

“Sleep disturbances are common in dementia but little is known about the various stages of sleep and whether they play a role in dementia risk,” said study author Matthew P. Pase, PhD, of Swinburne University of Technology in Australia in a news release. “We set out to discover which stages of sleep may be linked to dementia and while we did not find a link with deep sleep, we did with REM sleep.”

For the study, researchers monitored sleep cycles and patterns of 321 participants who are over the age of 60. They then collected the sleep data and then followed participants for an average of 12 years. During that time, 32 people were diagnosed with some form of dementia and of those, 24 were determined to have Alzheimer’s disease. They found that the participants who developed dementia spent an average of 17 percent of their sleep time in REM sleep, compared to 20 percent for those who did not.

Researchers also found that for every 1 percent reduction in REM sleep, the participants were 9 percent more likely to get dementia. The results withstand even after researchers adjusted for other factors that could affect dementia risk or sleep, such as heart disease factors, depression symptoms and medication use. They also noted that other stages of sleep were not associated with an increased risk of dementia risk.

“Our findings point to REM sleep as a predictor of dementia,” said Pase. “The next step will be to determine why lower REM sleep predicts a greater risk of dementia. By clarifying the role of sleep in the onset of dementia, the hope is to eventually identify possible ways to intervene so that dementia can be delayed or even prevented.”

The study, entitled “Sleep architecture and the risk of incident dementia in the community” has been published in the journal Neurology.