New research published on March 19, 2025, in the medical journal Neurology revealed a link between increased daytime sleepiness and a higher risk of dementia in elderly women. The study found that women in their 80s who experience increasing daytime sleepiness are more than twice as likely to develop dementia compared to those with stable sleep patterns.
The five-year study monitored 733 women aged 80 and above, tracking their sleep patterns and cognitive changes. Researchers aimed to examine how changes in sleep patterns over time were linked to the risk of developing dementia.
Among participants experiencing daytime sleepiness, the risk of developing dementia was twice as high as among those with stable sleep, even when accounting for factors like age, education level, race, and health issues. At the beginning of the study, all participants had normal cognition, with none having mild cognitive impairment or dementia.
As part of the study, all participants wore wrist devices for three days at the beginning and end of the study to measure their sleep and circadian rhythms. The researchers divided the women into three groups based on sleep patterns. Forty-four percent had stable sleep or slight improvement, 35 percent experienced decreased nightly sleep with reduced quality and duration, moderate increase in napping, and worsening circadian rhythms, and 21 percent had increased sleepiness.
During the study, 13% of the participants, amounting to 93 women, developed dementia. Among the participants who developed dementia, 8% had stable sleep patterns, 15% had declining nighttime sleep patterns, and 19% had increasing sleepiness. Interestingly, in the declining nighttime sleep group, no association with dementia risk was found, despite participants experiencing decreases in sleep quality and duration.
"Our study found that sleep problems may intertwine with cognitive aging and serve as an early marker or risk factor for dementia in women in their 80s," said Dr. Yue Leng, the lead researcher. "We observed that sleeping, napping, and circadian rhythms can change dramatically over only five years for women in their 80s," Leng commented, as reported by The Sun.
"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," Leng also stated, according to T-Online. Researchers emphasize that the study does not prove that daytime sleepiness causes dementia; it only shows an association between sleep changes and cognitive decline.
Researchers found an association between daytime sleepiness and dementia risk, which remained even after considering factors such as age, education level, body mass index, diabetes, hypertension, myocardial infarction, and antidepressant use. However, a limitation of the study was that it included primarily white participants, so the results cannot be generalized to more diverse populations.
The study was funded by the National Institutes of Health and the National Institute on Aging. The researchers conducted periodic cognitive tests and follow-ups throughout the study to monitor changes in the participants' cognitive health.
Sleep is crucial for neurological health, as it allows the brain to rest and rejuvenate, enhancing our ability to think clearly and remember information. Addressing sleep problems may help reduce the risk of developing dementia in the future.
Despite the findings, the study does not indicate a cause-and-effect relationship between sleepiness and dementia but suggests that sleep problems may be an early marker or risk factor. Researchers found a link between sleep problems and dementia but could not definitively say whether poor sleep causes dementia or whether the progressive breakdown of the brain leads to poor sleep quality.
The study adds to a body of recent UCSF-led research that shows poor sleep quality in midlife, delayed dream phase, and extended napping are linked to a higher risk of dementia. Recognizing and addressing sleep disturbances early might ultimately provide a valuable opportunity to intervene before cognitive decline advances.
Public health experts suggest the findings should influence how we approach aging and brain health at both individual and community levels. For women in particular, these findings highlight the importance of discussing sleep changes with healthcare providers rather than dismissing them as inevitable aspects of aging.
The UCSF research team plans follow-up studies to determine whether interventions targeting sleep can measurably reduce dementia rates. Deep sleep appears particularly important for clearing potentially harmful proteins from the brain, including those associated with Alzheimer's disease.
The article was written with the assistance of a news analysis system.