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Adults who report being very tired during the day are about three times more likely than those who don’t experience daytime sleepiness to have beta amyloid deposits in the brain — a hallmark of Alzheimer’s disease — years later, according to an analysis of data from the Baltimore Longitudinal Study of Aging. Researchers in the Department of Mental Health at Johns Hopkins Bloomberg School of Public Health and the National Institute on Aging conducted this analysis.

The Baltimore study was started in 1958 and followed the health of thousands of participants as they aged. From 1991 to 2000, participants completed a questionnaire asking:

• Do you often become drowsy or fall asleep during the daytime when you wish to be awake? (Yes or No)
• Do you nap? (Daily, 1-2 times/week, 3-5 times/week, or rarely/never)

Beginning in 2005, a subgroup of study participants had positron emission tomography (PET) scans using a radioactive compound that can identify beta amyloid deposits in the brain. After adjusting for other risk factors for daytime sleepiness (age, sex, education, body mass index, or BMI), the researchers discovered that Alzheimer’s risk, as indicated by beta amyloid deposits, was 2.75 times higher in people who had reported daytime drowsiness an average of 16 years earlier.