Have you been napping frequently for extended periods during the day or care for an older adult who might be doing so? A new study revealed that too much napping might be a sign of Alzheimer’s disease or early dementia.
Researchers from Harvard Medical School, UC San Francisco and Brigham and Women’s Hospital found older adults who napped at least once a day or more than an hour a day were 40% more likely to develop Alzheimer’s, compared to those who did not nap daily or napped less than an hour a day. The study was published in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
“Excessive napping could be a reflection of underlying Alzheimer’s disease pathology at the preclinical stage that affects the wake-promoting network and contributes to an increased daytime sleepiness,” Yue Leng, MD, PhD, co-senior author and assistant professor of psychology at the University of California San Francisco, told Seasons. “Excessive daytime napping might also impact and interact with nighttime sleep, resulting in altered 24-hour circadian rhythms, which have also been linked to an increased risk of Alzheimer’s.”
Why longer naps could be linked to Alzheimer’s disease/dementia
According to Leng, the researchers did not define a specific length of nap time but instead were more focused on the accumulated nap minutes per day and the change in the length of naps over the years.
Peng Li, PhD, first author and assistant professor of medicine at Harvard Medical School, told Seasons potential reasons why Alzheimer’s may be linked to longer or frequent naps.
“There is an extensive brain network that is responsible for keeping us awake, which is known as the ascending arousal system,” Li said. “Neurons within this network produce various neurochemicals that are essential for this arousal system to function properly to promote wake. Suppression of activity in the ascending arousal system will initiate sleep and help maintain sleep status.”
Li added tau tangles, one of the two hallmarks of AD pathology (the other is amyloid-beta) in those brain regions may decrease wake-promoting neurons, according to a prior study. Large accumulations of tau tangles and amyloid-beta proteins can slow a person’s ability to think and remember.
“Tau tangles may have decreased wake-promoting neurons in these brain regions, which may impair its normal function to promote wake, thus increasing the tendency of sleep,” Li explained.
Leng said while the loss of wake-promoting neurons could have led people to take longer naps, more evidence is needed to link longer/more frequent daytime napping and Alzheimer’s.
“I don’t think we have enough evidence to draw conclusions about causal relationships,” Leng said. “Rather, we think excessive or increased daytime napping might be used as a signal of accelerated aging or cognitive aging process that people should be cautious about.”
…excessive or increased daytime napping might be used as a signal of accelerated aging or cognitive aging process that people should be cautious about.
While it’s also unclear why too much sleep is associated with worse cognitive outcomes, Li said it’s likely that excess sleep may be a symptom of some coexisting health conditions that increase the risk of AD, dementia or underlying neurodegenerative processes.
How the study was conducted
Leng and her colleagues used data from the Rush Memory and Aging Project, which followed more than 1,400 people between the ages of 74 and 88 over 14 years. The researchers defined a nap as no movement for an extended period of time between 9 a.m. and 7 p.m.
Leng said participants also had to take “neuropsychological tests” to evaluate their cognition. At the beginning of the study, 75.7% of participants had no cognitive impairment (normal cognition), 19.5% had mild impairment, and 4.1% had Alzheimer’s disease.
Researchers found that longer and more frequent daytime naps were a risk factor for developing dementia in cognitively normal older men and women. Leng also noted as the disease progressed for participants, annual increases in the duration and frequency of napping advanced.
“For those with normal cognition, nap duration increased over time with an annual increase of 11 minutes per year,” she said. “The rate of increase doubled after the diagnosis of mild cognitive impairment (a total rate of 24 minutes per year) and a further tripling after the diagnosis of Alzheimer’s dementia (total rate of 68 minutes per year).”
The results reflect and support the findings from a 2019 study led by Leng that found older men who napped two hours a day raised the risk of cognitive impairment, compared to those who napped less than 30 minutes a day.
…older men who napped two hours a day raised the risk of cognitive impairment, compared to those who napped less than 30 minutes a day.
What can caregivers do?
Older adults and caregivers of people with Alzheimer’s should pay close attention to daytime napping behaviors and be cautious of an excessive or increased number of naps, Leng said.
In general, Li recommends older adults maintain a regular daily behavior pattern, including with nap and sleep. People should also seek further medical advice if they or a family member recognizes drastic changes in sleep behaviors.
People should also seek further medical advice if they or a family member recognizes drastic changes in sleep behaviors.
The authors noted because the study participants were older, the findings may not apply or translate to younger or middle-aged adults.