In a study of older adults, longer, more frequent daytime napping in a specific year predicted worse cognitive performance in the following year, and vice versa.
Daytime napping is common among older adults. The longitudinal relationship between daytime napping and cognitive aging, however, is unknown. A new cohort study by investigators from Brigham and Women’s Hospital found a bidirectional link between the two: excessive daytime napping predicted an increased future risk of Alzheimer’s dementia, and a diagnosis of Alzheimer’s dementia sped up the increase in daytime napping during aging. The team’s results are published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
“Daytime sleep behaviors of older adults are oftentimes ignored, and a consensus for daytime napping in clinical practice and health care is still lacking,” said Peng Li, PhD, of the Medical Biodynamics Program in the Brigham’s Division of Sleep and Circadian Disorders. “Our results not only suggest that excessive daytime napping may signal an elevated risk of Alzheimer’s dementia, but they also show that faster yearly increase in daytime napping may be a sign of deteriorating or unfavored clinical progression of the disease. Our study calls for a closer attention to 24-hour sleep patterns — not only nighttime sleep but also daytime sleep — for health monitoring in older adults.”
There are conflicting results regarding the effects of daytime napping on cognition in older adults. Whereas some studies have shown that daytime napping has benefits on acute cognitive performance, mood, and alertness, other studies have highlighted the adverse outcomes on cognitive performance. Nevertheless, researchers at the Brigham recognized that all prior studies on Alzheimer’s disease assessed napping within a participant only once, and most of them were subjective and questionnaire based. Therefore, they sought to conduct a longitudinal, objective assessment of naps to determine the link between daytime napping and Alzheimer’s dementia.
The current study tested two hypotheses: (1) Participants nap longer and/or more frequently with aging and the changes are even faster with the progression of Alzheimer’s dementia; and (2) participants with excessive daytime napping are at an increased risk of developing Alzheimer’s dementia.
The study was a collaborative work with Rush Alzheimer’s Disease Center and University of California, San Francisco. The team conducted its study using data from the on-going Rush Memory and Aging Project (MAP), a prospective, cohort study. Over 1,000 individuals, with an average age of 81, were provided Actical, a watch-like device, to wear on their non-dominant wrist for up to 14 days. The team identified sleep episodes using a previously validated sleep scoring algorithm that considers wrist activity counts. After napping episodes were identified, the nap duration and frequency were calculated.
Through the novel cohort study, researchers learned that nap duration and nap frequency were positively correlated with age and found a bi-directional, longitudinal relationship between daytime sleep and Alzheimer’s dementia. Independent of known risk factors for dementia, including age and nighttime sleep duration and fragmentation, longer and more frequent daytime naps were a risk factor for developing Alzheimer’s dementia in cognitively normal older men and women. Besides, annual increases in napping duration and frequency were accelerated as the disease progressed, especially after the clinical manifestation of Alzheimer’s dementia. Ultimately, the authors describe the relationship between daytime napping and cognition to be a “vicious cycle.”
“The vicious cycle we observed between daytime sleep and Alzheimer’s disease offers a basis for better understanding the role of sleep in the development and progression of Alzheimer’s disease in older adults,” said Li.
The authors acknowledge three primary study limitations. First, although actigraphy has been widely used in sleep field studies and validated, researchers recognize that polysomnography is the gold standard for sleep scoring. Second, the participants studied were older, and, therefore, the findings may not be easily translated to younger cohorts. Third, future studies should test whether a direct intervention in daytime napping can lower the risk of Alzheimer’s dementia or cognitive decline.
“Our hope is to draw more attention to daytime sleep patterns and the importance of patients noting if their sleep schedule is changing over time,” said co-senior author Kun Hu, PhD, of the Medical Biodynamics Program in the Brigham’s Division of Sleep and Circadian Disorders. “Sleep changes are critical in shaping the internal changes in the brain related to the circadian clocks, cognitive decline and the risk of dementia.”
Reference: “Daytime napping and Alzheimer’s dementia: A potential bidirectional relationship” by Peng Li, Lei Gao, Lei Yu, Xi Zheng, Ma Cherrysse Ulsa, Hui-Wen Yang, Arlen Gaba, Kristine Yaffe, David A. Bennett, Aron S. Buchman, Kun Hu and Yue Leng, 17 March 2022, Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
Funding: This work was supported by the NIH (RF1AG064312, RF1AG059867, R01AG56352, R01AG17917, T32GM007592, and R03AG067985), and the BrightFocus Foundation Alzheimer’s Research Program (A2020886S).
My husband is 80 years old this April. He owns and runs a golf course. In the winter when we are not as busy, he naps more. I have often wondered if he has early dementia because his memory is getting bad; but then, so is mine! However, when he goes back to work, he naps less as he doesn’t have enough time to nap. So, I am wondering if this study is an example of “correlation is not causation”. Perhaps those that nap more have less to do, which leads to less brain activity; and less chances to keep the brain stimulated.
Great comment, Nancy!
My mother was a very,very active woman, she never napped was up early 5 am bed 11 pm always on the go at 84 she was diagnosed with dementia age 95 she died.
My dad is 103 worked till about 2 years ago his hand didn’t help him. He does not have alzheimers/dementia he does not need seeing glasses or dentures. His brain is sharp his hearing not so well but he would used Q tips and regularly wash his ears.
My husband 81 was very active till 3 years ago he rolled down stairs. He naps a lot during day.I have noticed he has become lazy and he might be showing signs early dementia
As a scientific researcher myself, the findings in this study are not generalizable across any population other than that used in this specific study because study participates were not selected randomly. Though the author of the little article describing this study likely doesn’t know this, the findings of this study have very, very limited value in the scientific world…. but they do serve as a starting point. As such, let the reader not place much stock in study findings.
Thanks for the notice, Dr Herbert Barber.
The study has shown a correlation. But a vicious cycle I am so sure. Is a there a vicious cycle between age spots, loss of energy,thinning hair etc and Alzheimer’s.
The article keeps referring to excessive napping. What constitutes “excessive”?
Please define “excessive”!