Increasing sleepiness over 5 years doubled dementia risk among cognitively unimpaired women in their 80s.
Sleep efficiency, wake after sleep onset, and nap duration and frequency were individually linked with dementia.
Declining nighttime sleep was not associated with dementia.
Changes in sleep patterns among cognitively unimpaired women in their 80s were associated with an increased risk of dementia, a longitudinal study showed.
Compared with women who had stable sleep patterns, those who had increasing 24-hour sleepiness over 5 years had twice the odds of dementia (OR 2.21, 95% CI 1.14-4.26), reported Yue Leng, PhD, of the University of California San Francisco, and co-authors in Neurology.
Sleep profile parameters of sleep efficiency, wake after sleep onset, nap duration, and nap frequency were individually linked with dementia, but declining nighttime sleep was not. No associations were seen between sleep patterns and mild cognitive impairment.
The study is one of the first to examine longitudinal changes in multiple aspects of sleep patterns and their relationship with cognition, Leng noted.
"Our results showed that nighttime sleep, napping, and circadian rhythms can change dramatically over only 5 years for women in their 80s," she said.
"The change in daily sleep patterns may be intertwined with cognitive aging, and may serve as an early marker or risk factor for dementia in the oldest old," Leng told MedPage Today. "Our findings emphasize the importance of viewing sleep health both holistically and longitudinally."
The study results align with previous research, noted Marino Muxfeldt Bianchin, MD, PhD, and Eduardo Rigon Zimmer, PhD, both of the Universidade Federal do Rio Grande do Sul in Brazil.
By identifying shifts in sleep behavior as risk factors for dementia, the researchers "contribute to our understanding of the relationship between sleep and dementia, which can serve to conceptualize strategies for diagnosis, prevention, and treatment," Bianchin and Zimmer wrote in an accompanying editorial.
"Initiatives focusing on improving sleep efficiency, encouraging lifestyle changes, and implementing cognitive interventions may be essential in mitigating dementia risk in the aging population," they pointed out. "It is time to recognize the impact of sleep disturbances on dementia, as sleep is not just a rest period, but a foundation for cognitive well-being."
Many studies have examined the relationship between sleep and dementia, including Alzheimer's disease. Some experts believe the association is bidirectional.
Leng and colleagues studied 733 cognitively unimpaired women with a mean age of 82.5 who were enrolled in the prospective Study of Osteoporotic Fractures. All participants completed wrist actigraphy twice -- at baseline and follow-up -- and had their cognitive status evaluated at follow-up.
Through 24-hour actigraphy, the researchers identified three sleep-wake profiles:
Stable sleep (43.8% of participants) characterized by stability or small improvements
Declining nighttime sleep (34.9% of participants), which showed decreases in nighttime sleep quality and duration, moderate increases in napping, and worsening circadian rest-activity rhythms
Increasing sleepiness (21.3% of participants), which exhibited large increases in both daytime and nighttime sleep duration and quality, along with worsening circadian rest-activity rhythms
Over a follow-up period of 5 years, 12.7% of participants developed dementia and 22.4% developed mild cognitive impairment. The researchers adjusted findings to account for age, education, race, body mass index, diabetes, hypertension, myocardial infarction, antidepressant use, and baseline cognition.
Participants with at least one APOE4 allele showed worse changes in nighttime sleep parameters but better changes in napping and circadian rest-activity rhythms, "suggesting that the observed changes in these parameters may not only be markers of cognitive impairment but may be early risk factors," Leng and co-authors wrote.
The study was limited by its sample of women in their 80s who mainly were white, and findings may not apply to other populations, the researchers acknowledged. Cognitive assessments occurred at the same point as the second sleep evaluation, and changes in cognition and sleep may have occurred in parallel, they added.
Concurrent declines in sleep and cognition may exacerbate each other, accelerating deterioration in both domains, the researchers noted.
"Future studies should look at all aspects of daily sleep patterns to better understand how changes in these patterns over time are linked to dementia risk," Leng said.
Judy George covers neurology and neuroscience news for MedPage Today, writing about brain aging, Alzheimer’s, dementia, MS, rare diseases, epilepsy, autism, headache, stroke, Parkinson’s, ALS, concussion, CTE, sleep, pain, and more. Follow
Disclosures
This study was supported by the National Institute on Aging.
Leng and co-authors reported no disclosures.
The editorialists reported no disclosures.
Primary Source
Neurology
Source Reference: Milton S, et al "Five-year changes in 24-hour sleep-wake activity and dementia risk in oldest old women" Neurology 2025; DOI: 10.1212/WNL.0000000000213403.
Secondary Source
Neurology
Source Reference: Bianchin MM, Zimmer ER "Wake-up call: the association between sleep disturbances and dementia" Neurology 2025; DOI: 10.1212/WNL.0000000000213516.