Increased daytime sleepiness could raise the risk of dementia among women in their eighties, neurologists have warned.
A study found that female octogenarians who experience increased daytime sleepiness over a five-year period may have double the risk of developing dementia.
"Sleep is essential for cognitive health, as it allows the brain to rest and rejuvenate, enhancing our ability to think clearly and remember information," said study author Yue Leng, PhD, of the University of California, San Francisco, in a statement.
"However, little is known about how changes in sleep and cognition are connected over time and how these changes relate to dementia risk in the later decades of life.
"Our study found that sleep problems may be intertwined with cognitive aging and may serve as an early marker or risk factor for dementia in women in their 80s."
How the Research Was Conducted
Researchers followed 733 female participants with an average age of 83 who did not have mild cognitive impairment or dementia at the beginning of the study.
Over a five-year period, 164 participants (22%) developed mild cognitive impairment, while 93 participants (13%) developed dementia.
To assess sleep patterns, participants wore wrist devices that tracked their sleep duration, quality, and circadian rhythm patterns for three days at the start and end of the study.
Researchers examined changes in nighttime sleep, daytime napping, and circadian rhythms over the five-year period and identified three distinct sleep pattern groups:
- Stable or improving sleep (44%);
- Declining nighttime sleep (35%), which included reduced sleep duration and quality, moderate increases in napping, and worsening circadian rhythms;
- Increasing sleepiness (21%), characterized by increased nighttime and daytime sleep duration and quality, along with worsening circadian rhythms.
Link Between Sleep Patterns and Dementia Risk
When researchers analyzed how these sleep pattern changes correlated with dementia risk, they found that.
- In the stable sleep group, 8% (25 participants) developed dementia.
- In the declining nighttime sleep group, 15% (39 participants) developed dementia.
- In the increasing sleepiness group, 19% (29 participants) developed dementia.
After adjusting for factors such as age, education, race and health conditions like diabetes and high blood pressure, researchers found that women in the increasing sleepiness group had double the risk of developing dementia compared to those in the stable sleep group.
However, no significant link was found between the declining nighttime sleep group and dementia risk.
"We observed that sleeping, napping, and circadian rhythms can change dramatically over only five years for women in their 80s," Leng said.
"This highlights the need for future studies to look at all aspects of daily sleep patterns to better understand how changes in these patterns over time can be linked to dementia risk."
A limitation of the study was that the participants were predominantly white, meaning the findings may not be generalizable to more diverse populations.
Reducing Dementia Risk
While sleep patterns may indicate an increased risk of dementia, certain lifestyle changes can help lower the likelihood of developing the condition. According to the Alzheimer's Society, strategies to reduce dementia risk include:
- Staying physically active: Regular exercise improves blood flow to the brain and supports cognitive function;
- Keeping mentally and socially engaged: Activities like reading, puzzles, and socializing with others stimulate the brain;
- Managing health conditions: Controlling blood pressure, cholesterol, and diabetes can lower dementia risk;
- Drinking Less Alcohol: Drinking in moderation—no more than 14 units each week—to lower risk of damage to organs which can.
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Reference
Milton, S., Cavaillès, C., Ancoli-Israel, S., Stone, K. L., Yaffe, K., & Leng, Y. (2025). Five-Year Changes in 24-Hour Sleep-Wake Activity and Dementia Risk in Oldest Old Women. Neurology, 104(8). https://doi.org/10.1212/WNL.0000000000213403