Sleep disturbance is common in dementia, but the reason is unclear.

Getting less REM sleep — the phase in which we dream — is linked to dementia, a study finds.

During sleep the brain cycles between periods of deep sleep and then up towards shallower periods of sleep in which we tend to dream, whether we remember those dreams or not.

During REM sleep the eyes move rapidly from side-to-side (hence Rapid Eye Movement Sleep).

Brain activity also increases and our pulses quicken.

Dr Matthew P. Pase, the study’s first author, said:

“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.

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.”

The research involved 321 people, average age 67, who were followed for 12 years.

The results showed that people who eventually developed dementia spent less time in REM sleep than those that did not.

For each 1% decrease in REM sleep, the dementia risk increased 9%.

In this study, average REM sleep for those that did not develop dementia was 20%.

For those that did develop dementia it was 17%.

Dr Pase said:

“Our findings point to REM sleep as a predictor of dementia.

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 other stages of sleep were not linked to dementia, the researchers found.

The study was published in the journal Neurology (Pase et al., 2017).