April 2, 2025
Among the elderly, feeling sleepy much of the time may be an early warning sign of Alzheimer’s disease, according to a new report. The study found that in cognitively healthy women in their 80s, those who experienced increasing sleepiness over a five-year period had double the risk of developing Alzheimer’s disease or other forms of dementia compared to their peers who did not feel increasingly drowsy.
The findings add to growing evidence of the links between sleep disturbances and Alzheimer’s disease. Feeling excessively tired during the day is often a sign of poor sleep the night before. Even people who might think they got a decent night’s sleep may feel sleepy much of the time because of problems like sleep apnea, which causes people to wake up for brief periods during the night, or other sleep problems.
“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 of the University of California, San Francisco. “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.”
This study looked only at older women, and it showed only an association between daytime sleepiness and increased dementia risk so cannot prove cause and effect. But other studies have found links between sleep disturbances and an increased risk of memory problems and dementia in younger women and men as well.
For the study, researchers looked at 733 women who were enrolled in a study of aging and bone fractures. Their average age was 83. None had serious memory problems at the start of the study.
The women wore watch-like wrist devices to track their sleep and waking patterns for three days at the beginning of the study and again at the end, five years later. The devices tracked how long they slept during the night, how sound their sleep was, how many naps they took during the day, and their general sleep-wake patterns.
The researchers found that more than half the women experienced significant changes in their sleep and waking patterns during the study period. Three main sleep patterns emerged. About 44 percent of the women experienced stable sleep or small improvements in sleep over the five-year study period. About a third (35 percent) showed declines in nighttime sleep, including sleeping less soundly and for shorter periods during the night but had moderate increases in how much they napped during the day. And about one in five (21 percent) exhibited signs of increasing sleepiness, including sleeping and napping more throughout the day and night, with less sound sleep and more fractured sleep patterns.
By the end of the study, 93 of the women, or about 13 percent, developed Alzheimer’s disease or other form of dementia. Another 164, or 22 percent, developed mild cognitive impairment, a brain disorder marked by serious memory loss that often progresses to full-blown dementia.
After considering various risk factors for dementia such as age, level of education and medical conditions like high blood pressure and diabetes, the researchers calculated that women in the increasing sleepiness group doubled their risk of developing dementia while stable sleep behavior was associated with a decreased risk of dementia. Among those who experienced increasing sleepiness, 19 percent developed Alzheimer’s or other form of dementia, compared to only 8 percent in the stable sleep group.
Declining nighttime sleep had a less prominent effect on heightened dementia risk. About 15 percent of those in the declining nighttime sleep group developed dementia. Changes in sleep patterns were not tied to risk of mild cognitive impairment in this study. The findings were published in Neurology, the medical journal of the American Academy of Neurology.
The findings underscore the importance of sound sleep for brain health. Earlier research has found, for example, that men and women in their 30s and 40s who tend to have disrupted sleep, waking up numerous times during the night, are at higher risk of developing memory and thinking problems later in life. Older people who have sleep disturbances show signs of brain changes typical of Alzheimer’s disease. Sound sleep at night may help to clear the brain of toxic beta-amyloid, a protein that builds up in the brains of those with Alzheimer’s disease, while poor sleep may promote its accumulation.
Experts stress the importance of daily habits to help promote sounder sleep. Suggested measures include going to bed and waking up at the same time each day, even on weekends; minimizing the use screens and electronic devices, which can emit blue light that disrupts levels of the sleep hormone melatonin, near bedtime; avoiding alcohol or caffeine late in the day; taking time to relax and unwind before going to bed; and getting some sunshine and exercise during the day. Psychological approaches like cognitive behavioral therapy, or CBT, which teaches people to challenge negative or stressful thoughts at bedtime, can also help.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D. Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Sources: Sasha Milton, Clemence Cavailles, Sonia Ancoli-Israel, et al: “Five-Year Changes in 24-Hour Sleep-Wake Activity and Dementia Risk in Oldest Old Women.” Neurology, March 19, 2025
Marino Muxfeldt Bianchin, Eduardo Rigon Zimmer: “Wake-Up Call: The Association Between Sleep Disturbances and Dementia” (editorial). Neurology, March 19, 2025.
