24 August, 2017
Upon follow-up, the researchers found that each percentage reduction in REM sleep was associated with a nine percent increase in the risk of all-cause dementia and an eight percent increase in the risk of Alzheimer's disease dementia. During that study, sleep cycles were measured for each participant.
A lack of REM sleep could also be a sign of stress, which causes people to be more easily disturbed at night, something which is also linked to dementia.
More than 5 million Americans have Alzheimer's and the number is expected to grow as the population ages.
Previous study had revealed that people who consistently sleep more than nine hours each night had double the risk of developing dementia in 10 years as compared to participants who slept for nine hours or less.
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. During that time, 32 people were diagnosed with some form of dementia and of those, 24 were determined to have Alzheimer's disease. "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".
For their study, the U.S. researchers monitored the sleeping patterns of 321 participants over the age of 60.
It wasn't a big difference.
And so spending just 1 per cent less time in this stage, also called the rapid eye movement (REM) stage, has been linked to a 9 per cent increase in dementia risk, a study has found.
"Our findings point to REM sleep as a predictor of dementia", Pase said in a statement.
Other stages of sleep were not associated with an increased dementia risk.
Sleep disturbance has always been recognized as being common in dementia, but it's not clear if differences in sleep architecture precede dementia onset, the researchers said.
'The next step will be to determine why lower REM sleep predicts a greater risk of dementia'.
There are several possibilities.
"REM sleep may also buffer against synaptic loss and cognitive decline by assisting in the production of new connections and networks".
The investigators concluded that deep sleep patterns had no bearing on dementia risk.
"Many older adults without dementia also notice changes in their sleep, but these disturbances occur more frequently and tend to be more severe in Alzheimer's".
Sleep moves through five distinct phases each night: light sleep; a pre-deep sleep preparatory phase; two subsequent stages of deep sleep; and finally REM sleep.
According to Osorio, "We know that [REM sleep] is important for the survival of most mammalian and avian species" and also appears to help facilitate memory function and infant brain development.
