Daily napping among older adults linked to a 40% higher risk for Alzheimer’s disease
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Older adults who nap for more than an hour a day had a 40% higher risk for developing Alzheimer’s disease compared with those who napped less than an hour a day, researchers reported in Alzheimer’s & Dementia.
In addition, those who napped at least once a day had a 40% higher risk for developing AD compared with those who did not nap once a day, Yue Leng, PhD, assistant professor of psychiatry at the University of California San Francisco (UCSF) Weill Institute for Neurosciences, and colleagues reported. They evaluated the longitudinal relationship between daytime napping and cognitive aging.
“We found the association between excessive daytime napping and dementia remained after adjusting for nighttime quantity and quality of sleep,” Leng, co-senior author of the study, said in a UCSF press release. “This suggested that the role of daytime napping is important itself and is independent of nighttime sleep.”
Leng and colleagues assessed 1,401 participants, who had a median age of 81 years, through the Rush Memory and Aging Project at the Rush Alzheimer’s Disease Center in Chicago. The center monitored participants for up to 14 years.
Participants wore a watch-like device that tracked mobility for up to 14 days each year and underwent a series of annual neuropsychological tests that evaluated cognition. At baseline, 75.7% of participants had no cognitive impairment, 19.5% had mild cognitive impairment, and 4.1% had AD.
According to study results, daily napping increased by an average of 11 minutes per year for participants who did not develop cognitive impairment. Following a diagnosis of mild cognitive impairment, napping increased to an average of 24 minutes, and this continued to increase to 68 minutes after a diagnosis of AD.
When evaluating participants who had normal cognition at baseline but developed AD after 6 years, as well as those who had stable cognition throughout the trial, Leng and colleagues observed that longer daytime naps were associated with a higher risk for developing Alzheimer’s dementia (HR = 1.2; 95% CI, 1.06-1.35). Further, more frequent naps also were associated with a higher risk for Alzheimer’s dementia (HR = 1.23; 95% CI, 1.08-1.39).
“I don’t think we have enough evidence to draw conclusions about a causal relationship, that it’s the napping itself that caused cognitive aging, but excessive daytime napping might be a signal of accelerated aging or cognitive aging process,” Leng said. “It would be very interesting for future studies to explore whether intervention of naps may help slow down age-related cognitive decline.”