Women in their 80s who become sleepier during the day over several years may have a higher risk of developing dementia, according to a new study published in Neurology®, the journal of the American Academy of Neurology.
The research found that women who showed increasing daytime sleepiness over five years had double the risk of getting dementia compared to women with stable sleep patterns. However, the study only shows a connection—it does not prove that sleepiness causes dementia.
“Sleep is important for brain health,” said study author Dr. Yue Leng from the University of California, San Francisco. “It helps the brain rest and recharge, which supports thinking and memory. But we still don’t fully understand how sleep and memory problems are related over time, especially in older age.”
The study included 733 women, with an average age of 83, who had no signs of memory loss or dementia at the start. Over five years, researchers followed these women to track their sleep and cognitive health. During the study, 164 women developed mild memory problems, and 93 were diagnosed with dementia.
To track sleep, the participants wore wrist devices that recorded their sleeping patterns and body rhythms at the beginning and end of the five years. The researchers focused on changes in how long and how well the women slept at night, how much they napped during the day, and changes in their natural daily rhythms (circadian rhythms).
After five years, more than half of the women (56%) had big changes in their sleep. The researchers divided them into three groups based on these changes:
44% had stable or slightly better sleep
35% had worse nighttime sleep (shorter sleep, more waking up at night, more napping)
21% had increased sleepiness (more sleeping both day and night, lower quality sleep, worse body rhythms)
The team then looked at how these changes affected the risk of developing dementia. In the stable sleep group, 8% developed dementia. In the group with worse nighttime sleep, 15% developed dementia. In the increasing sleepiness group, 19% developed dementia.
After adjusting for age, race, education, and health issues like diabetes and high blood pressure, the researchers found that women in the increasing sleepiness group had twice the risk of developing dementia compared to the stable sleep group. Interestingly, the group with worse nighttime sleep did not have a higher dementia risk.
Dr. Leng noted that the study shows how much sleep and daily rhythms can change in just a few years for women in their 80s. She believes future research should look at all parts of sleep—including naps, sleep quality, and daily rhythms—to better understand their link to dementia risk.
One limitation of the study was that most participants were white, so the results may not apply to more diverse groups. The study was funded by the National Institutes of Health and the National Institute on Aging.
If you care about dementia, please read studies about dietary strategies to ward off dementia, and how omega-3 fatty acids fuel your mind.
For more health information, please see recent studies about Choline deficiency linked to Alzheimer’s disease, and what to eat (and avoid) for dementia prevention.
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