A ground-breaking study by a Swinburne researcher has found that dementia in the elderly can be predicted by measuring rapid eye movement (REM) sleep.
The study, to be published in the latest online issue of Neurology, found that for every per cent that REM sleep was reduced in an elderly person, there was a nine-fold increase in the risk of them developing dementia.
Author, Dr Matthew Pase, says the findings point to REM sleep being a predictor of 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,” Dr Pase said.
“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.”
During the REM stage, the eyes move more rapidly and there is increased brain activity along with quicker pulse and faster breathing. This stage usually occurs about an hour to an hour-and-a-half into sleep and then recurs throughout the night as the cycles repeat.
REM sleep is the fifth sleep stage and happens before dreaming occurs:
- Stage one: light sleep
- Stage two: the body begins to prepare for deep sleep
- Stages three and four: deep sleep
- Stage five: REM sleep
Dr Pase is an NHMRC Sidney Sax Senior Research Fellow at Swinburne’s Centre for Human Psychopharmacology and a visiting Research Scholar at the Department of Neurology, Boston University School of Medicine.
Gathering the data
For the study, researchers looked at 321 people with an average age of 67 who participated in the US based Framingham Heart Study.
During the study, their sleep cycles were measured. Researchers then followed the 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.
Those who developed dementia spent an average of 17 per cent of their sleep time in REM sleep, compared to 20 percent for those who did not develop dementia.
After adjusting for age and sex, researchers found that a lower percentage of REM sleep and a longer time to get to the REM sleep stage were both linked to a greater risk of dementia.
The results were similar after researchers adjusted for other factors that could affect dementia risk or sleep, such as heart disease factors, depression symptoms and medication use.
Other stages of sleep were not associated with an increased dementia risk.
“The next step will be to determine which mechanisms of REM sleep lead to the 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 was supported by the National Heart, Lung and Blood Institute, the National Institute on Aging and the National Institute for Neurological Disorders and Stroke.