REM Sleep Tied to Dementia Risk

Spending less time in REM sleep may be associated with a greater risk of dementia, researchers found.

In a prospective cohort study, each percentage reduction in REM sleep was tied to a 9% increase in dementia risk (HR 0.91, 95% CI 0.86-0.97, P=0.004), reported Matthew Pase, PhD, of Swinburne University of Technology in Australia, and colleagues online in Neurology.

"Our findings point to REM sleep as a predictor of dementia," Pase said in a statement.

Sleep disturbance has long been recognized as being common in dementia, but it's not clear if differences in sleep architecture precede dementia onset, the researchers said. To get a better understanding of the relationship, they studied 321 people from the Framingham Heart Study-Offspring cohort who participated in the Sleep Heart Health Study from 1995 to 1998.

Participants were a mean age of 67 when they had sleep assessment, and they were followed for a mean of 12 years. During that time, 32 were diagnosed with dementia, and of those, 24 had Alzheimer's disease.

Overall, Pase's group found an association between diminished REM sleep and dementia risk: those who developed dementia spent 17% of their sleep time in REM sleep compared with 20% for those who didn't have dementia.

In adjusted models, REM sleep was associated with both dementia risk and Alzheimer's disease risk. One model was adjusted for age and sex, and the other for those two factors plus BMI, education, APOE4 status, smoking status, systolic blood pressure, hypertension treatment, diabetes, heart disease, depressive symptoms, sleep medication use, antidepressant use, and anxiolytic use.

Indeed, for every percent reduction in REM sleep, there was a 9% increase in dementia risk (HR 0.91, 95% CI 0.86-0.97, P=0.004 and HR 0.91, 95% CI 0.85-0.98, P=0.01 in each model).

The researchers also found that the lowest versus highest tertile of REM sleep latency was associated with a lower risk of all-cause dementia in both models (HR 0.37, 95% CI 0.14-0.97 and HR 0.26, 95% CI 0.08-0.85, respectively).

Higher wake-after-sleep-onset was associated with an increased risk of dementia in only one model, and although higher total sleep time was associated with a lower risk of all-cause dementia and AD dementia in one of the models, the effect sizes were small.

Non-REM sleep stages, as well as sleep onset latency, sleep efficiency, and the AHI, were not related to dementia, the researchers noted.

"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," Pase said in a statement. "While we did not find a link with deep sleep, we did with REM sleep."

Pase's group said the mechanisms linking REM sleep to dementia aren't known, but cholinergic neurons are important determinants of REM sleep. Alzheimer's is known to be associated with loss of cholinergic function, which may underpin the association between reduced REM sleep and dementia risk, they wrote.

They cautioned that the study was limited by its small sample size, and that larger studies are needed to confirm the findings.

"The next step will be to determine why lower REM sleep predicts a greater risk of dementia," Pase said in a statement. "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.