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Daytime Sleepiness Tied to Alzheimer’s Brain Changes

A long-term study of aging men and women found that those who said they were often very sleepy during the day were nearly three times more likely than those who were not sleepy to have brain changes typical of Alzheimer’s disease. The findings add to a growing body of evidence linking sleep troubles with Alzheimer’s disease.

“Factors like diet, exercise and cognitive activity have been widely recognized as important potential targets for Alzheimer’s disease prevention, but sleep hasn’t quite risen to that status — although that may well be changing,” said Adam P. Spira, the study leader and an associate professor in the department of mental health at the Johns Hopkins Bloomberg School of Public Health. “If disturbed sleep contributes to Alzheimer’s disease, we may be able to treat patients with sleep issues to avoid these negative outcomes.”

For the study, published in the journal SLEEP, researchers used data from the large and ongoing Baltimore Longitudinal Study of Aging, which began in 1958 and recorded the health of thousands of men and women as they aged. During the 1990s, study volunteers completed a questionnaire that asked a variety of simple questions, including: “Do you often become drowsy or fall asleep during the daytime when you wish to be awake?” and “Do you nap?”

Participants responded with a variety of choices: “Daily,” “1 to 2 times a week,” “3 to 5 times a week,” or “rarely or never.”

More than 15 years later, some of the volunteers also got PET scans of their brains to look for signs of Alzheimer’s disease. The scans used a compound called “Pittsburgh compound B” that acts as a dye and allows doctors to detect deposits of beta-amyloid, a toxic protein that builds up and forms amyloid plaques in the brains of those with Alzheimer’s disease.

The researchers found that those who reported daytime sleepiness years earlier were nearly three times more likely to have beta-amyloid buildup in the brain than those who did not report daytime sleepiness. They controlled for factors like age, sex, education level and weight, and still the increased risk of beta-amyloid accumulation for those with sleep problems persisted.

Volunteers who reported napping were also more likely to have beta-amyloid buildup than those who did not nap, though the results were not statistically significant.

Earlier studies have shown that poor sleep can lead to memory and thinking problems, even in healthy people. Lack of sleep or waking up several times during the night has also been shown to be bad for the brain and increase the risk of Alzheimer’s disease. People with a common breathing disorder called sleep apnea, which causes sleepers to awaken briefly hundreds of times during the night, has also been linked to memory problems and an increased risk of dementia.

And it’s long been known that people with Alzheimer’s disease tend to sleep poorly and spend more time awake at night. But scientists have been uncertain whether poor sleep contributes to Alzheimer’s onset, or if troubled sleep is actually an early symptom of Alzheimer’s. It is possible, for example, that high levels of beta-amyloid in the brain may disrupt sleep.

Still, scientists are uncertain why daytime sleepiness and poor sleep may be tied to the buildup of beta-amyloid in the brain. Previous studies suggest that one reason is that sleep may help to clear toxic molecules from the brain.

But poor sleep, as well as sleep apnea, is a common problem in the elderly. Just because you don’t sleep well or feel drowsy during the day doesn’t mean you will get Alzheimer’s disease.

A sound night’s sleep, though, may be a critical component of a healthy lifestyle — and might even help to keep Alzheimer’s at bay. “There is no cure yet for Alzheimer’s disease, so we have to do our best to prevent it” Dr. Spira. “Even if a cure is developed, prevention strategies should be emphasized. Prioritizing sleep may be one way to help prevent or perhaps slow this condition.”

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Adam P. Spira, Yang An, Mark N. Wu, Jocelynn T. Owusu, et al: “Excessive Daytime Sleepiness and Napping in Cognitively Normal Adults: Associations with Subsequent Amyloid Deposition Measured by PiB PET. ” Sleep, September 2018.

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