A common complaint heard in offices or classrooms is that people don’t get enough sleep. Causes range from taking care of an infant, staying up late to watch the latest episode of a television show or studying long hours at the library. But what if there were such a thing as too much sleep or not enough of the right kind of sleep?
BUSM researchers published findings in the journal Neurology that show spending less time in REM (rapid eye movement) sleep and taking longer to enter REM sleep are associated separately with a higher risk of developing dementia.
On average humans spend approximately one-third of their life, or about eight hours per night, sleeping. Sleep is categorized into both non-REM and REM sleep and it is REM sleep that is thought to be responsible for memory consolidation. REM sleep accounts for only a quarter of total sleep time.
Using data from the Framingham Heart Study (FHS), researchers studied 321 participants over the age of 60 who participated in an overnight sleep study between 1995 and 1998. They then were followed for an average of 12 years to determine their risk of developing dementia. 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.
“Different stages of sleep may differentially affect key features of Alzheimer’s disease. Our findings implicate REM sleep mechanisms as predictors of dementia,” explained lead author Matthew Pase, PhD, BUSM neurology fellow and FHS investigator.
Earlier this year, Pase and his colleagues found 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. Those findings also were reported in Neurology.
They added that future research is needed to determine whether REM sleep helps protect the brain from dementia or is sensitive to early brain changes that accompany dementia.
Submitted by Robert Martin, MD.