Daytime napping among older people is a normal part of aging but it may also be a sign of Alzheimer’s disease and other dementias, stated a study led by UC San Francisco and Harvard Medical School together with Brigham and Women’s Hospital.
Once dementia or its usual precursor, mild cognitive impairment, are diagnosed, the frequency or duration of napping accelerates rapidly. Dementia may affect the wake-promoting neurons in key areas of the brain, the researchers stated in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
In the study, the researchers analyzed data from 1,401 seniors, who had been monitored for up to 14 years by the Rush Memory and Aging Project at the Rush Alzheimer’s Disease Center in Chicago. The participants, whose average age was 81 and of whom approximately three-quarters were female, wore a watch-like device that tracked mobility. Each prolonged period of non-activity from 9 AM to 7 PM was interpreted as a nap.
“We found the association between excessive daytime napping and dementia remained after adjusting for nighttime quantity and quality of sleep. This suggested that the role of daytime napping is important itself and is independent of nighttime sleep,” said co-senior author Ms. Yue Leng, MD, Ph.D., of the UCSF Department of Psychiatry and Behavioral Sciences.
The device was worn every year continuously for up to 14 days, and once a year each participant underwent a battery of neuropsychological tests to evaluate cognition. At the start of the study, 75.7 percent of participants had no cognitive impairment, while 19.5 percent had mild cognitive impairment and 4.1 percent had Alzheimer’s disease.
The researchers confirmed that participants who napped more than an hour a day had a 40 percent higher risk of developing Alzheimer’s than those who napped less than an hour a day, and participants who napped at least once a day had a 40 percent higher risk of developing Alzheimer’s than those who napped less than once a day.