THE ARISING · Longevity & Healthspan
Napping Most Days Linked to 48% Higher Dementia Hazard in Older Adults
Older adults who napped most days had a 48% higher hazard of developing dementia over the next decade than those who rarely or never napped. Falling asleep without meaning to carried a separate, slightly smaller 39% higher hazard. That is the finding of a new study in The Journals of Gerontology: Series A. It is an association, not proof of cause. Our own view, which the study does not test, is that frequent or unplanned daytime sleep may be worth raising with a doctor, not only changing as a habit.
This is an observational study in people. It cannot show that napping causes dementia. Researchers at the Johns Hopkins Bloomberg School of Public Health used data from the National Health and Aging Trends Study, a survey of U.S. Medicare beneficiaries aged 65 and older. The analysis included 995 participants who showed no sign of possible or probable dementia in 2013. They were followed up to 2023.
In 2013, participants answered questions about their napping. Those who said they napped "never" or "rarely" were counted as non-nappers. Those who napped "some days" were infrequent nappers. Those who napped "most days" or "every day" were frequent nappers. Participants were also asked whether naps were planned or whether they fell asleep without meaning to. They were asked how long naps usually lasted, either 30 minutes or less, or more than 30 minutes.
Dementia was identified at each yearly round by a validated algorithm, not by a clinical exam. The outcome was "possible or probable" dementia. Possible dementia meant impairment in one area of thinking. Probable dementia meant a reported diagnosis, an informant report of dementia, or impairment in at least two areas.
Compared with non-nappers, frequent nappers had 1.48 times the hazard of developing possible or probable dementia (95% confidence interval 1.14 to 1.94). Unintentional napping was also linked to higher risk (hazard ratio 1.39; 95% CI 1.06 to 1.81). Infrequent napping and intentional napping showed no association.
The results for length were less clear. Naps of 30 minutes or less were linked to higher risk (hazard ratio 1.40; 95% CI 1.06 to 1.85). Naps longer than 30 minutes were not clearly linked once the analysis also adjusted for sleep factors (hazard ratio 1.28; 95% CI 0.96 to 1.69). So the study does not show that short naps are worse than long ones.
The analysis adjusted for age, sex, race and ethnicity, education, smoking, body mass index, number of health conditions, depressive and anxiety symptoms, nighttime sleep duration, daytime sleepiness and risk of obstructive sleep apnea, a breathing disorder that disrupts sleep.
The authors also tried to address reverse causation, meaning that early brain changes might cause the napping rather than the reverse. They excluded dementia cases in the first five years of follow-up. According to Neuroscience News, which covered the study, the associations for frequent and unintentional napping held steady. The coverage went further than the study in saying this shows napping changes emerge years before diagnosis. The paper itself describes napping as possibly a risk factor "if supported by further evidence."
The paper notes that napping may reflect disease rather than drive it. For example, damage to wake-promoting brain cells linked to tau pathology can cause excessive daytime sleepiness. "More frequent napping could be a marker of changes in the brain, rather than a cause of brain changes that lead to dementia," senior author Adam Spira told Neuroscience News.
For you
What does this mean for personal health? The study does not show that cutting back on naps lowers dementia risk. The paper notes that naps can result from disturbed nighttime sleep, including undiagnosed sleep disorders. Our suggestion, not a finding of the study, is that falling asleep without meaning to, or a new pattern of napping most days, is worth raising with a doctor, who can look for causes such as sleep apnea or other health problems. The study did not test any such steps, and this is the weakest link in the argument.
The study has limits. Napping was self-reported at one point in 2013. Dementia was classified by algorithm. The sample was limited to those who answered the sleep module, and those left out of the main analysis were older, had lower education and more depressive and anxiety symptoms. The authors call for studies with more detailed napping measures and longer follow-up.
Lead author Kening Jiang said, according to Neuroscience News, that monitoring napping could be an early and accessible marker of higher risk. The study was supported in part by the National Institute on Aging. What to watch next: studies that track napping with wearable sensors and test whether treating poor sleep changes cognitive outcomes.
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