Excessive sleeping on a regular basis may predict the onset of dementia. Photo courtesy of Pixabay, Public Domain

Sleep is a good indicator of our overall health and well-being. Seven to nine hours of sleepis recommended to feel truly rested, but oversleeping on a regular basis could signal problems with our brain health. A study published in Neurology found people who consistently sleep more than nine hours a night are more likely to develop dementia accompanied by smaller brain volume, and poor executive function.

“Participants without a high school degree who sleep for more than 9 hours each night had six times the risk of developing dementia in 10 years as compared to participants who slept for less," said Dr. Sudha Seshadri, corresponding study author, and professor of neurology at Boston University School of Medicine Alzheimer's Disease Center (BUSM) and Framingham Heart Study (FSH) senior investigator, in a statement.

Previous research suggests both too little sleep and too much sleep are linked to dementia. Missing out on deep non-REM (rapid eye movement) sleep may allow proteins linked to dementia to have easier access to the brain. Beta-amyloid, a protein suspected of triggering Alzheimer's, aggregates in higher concentrations in the brains of those who chronically suffer from poor sleep. As beta-amyloid accumulates, the protein further inhibits the ability to sleep, which feeds into a terrible cycle linked to dementia.

Researchers have also found education levels can affect the likelihood of developing dementia. Studies on dementia have consistently showed the more time spent in education, the lower the risk of developing the neurodegenerative disease. It seems people with more education are better able to compensate for the effects of dementia. Education in early life appears to help people cope with a lot of changes in their brain before showing dementia symptoms.

Now, Seshadri and her colleagues at Boston University School of Medicine Alzheimer's Disease Center provide further evidence longer sleep duration may be a marker of early neurodegeneration.

Close to 2,500 participants, with an average age of 72, self-reported total hours of sleep: six hours was categorized as short; six to nine hours was a reference pointed; and more than nine hours are categorized as long. They were asked about their sleep duration twice, 13 year apart, to determine how sleep duration affected dementia risk over time. During the years of follow-up, 234 cases of all-cause dementia were observed, and 181 cases were clinically consistent with Alzheimer's disease.

The findings revealed elderly people who consistently slept more than nine hours a night had double the dementia risk over a decade of follow-up. Excessive sleepers had smaller brain volumes and exhibited poor executive function. Moreover, participants without high school degrees who slept more than nine hours a night, had six times the risk of developing dementia, compared to those who slept less than nine hours a night.