Frequent Daytime Napping May Signal Higher Dementia Risk in Older Adults, Study Finds

The study begins with a simple question put to older Americans: how often do you nap during the day? Researchers at Johns Hopkins University took the answers from 995 participants in the National Health and Aging Trends Study, a longitudinal survey of Medicare beneficiaries aged 65 and older, and then waited to see who developed dementia.

None of the 995 had probable or possible dementia when the study began. Over a median follow-up of five years, 417 of them, or 41.9 percent, were classified as having developed possible or probable dementia. The findings appeared in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences.

The central result concerns frequency. People who said they napped every day or most days had a 48 percent higher rate of dementia than people who never or rarely napped. That comparison held after the team adjusted for age, sex, race and ethnicity, education, smoking status, body mass index, and a range of health conditions and sleep factors.

The kind of nap mattered too. Unintentional napping, the dozing off that happens without planning, was linked to a 39 percent higher dementia rate than among non-nappers. Naps of 30 minutes or less were tied to a 40 percent higher rate. Frequent, unintentional, and short napping were also associated with a higher risk of developing memory impairment during follow-up.

The researchers also saw signs of elevated risk with infrequent napping, intentional napping, and naps longer than 30 minutes. After adjustment in the final analysis, however, those effects were not statistically significant.

The authors are careful about what the numbers can carry. The study is observational, so it cannot show that napping causes dementia. Adam Spira, a psychologist and sleep researcher at Johns Hopkins, put it this way: more frequent napping could be a marker of changes in the brain, rather than a cause of the changes that lead to dementia. In their paper, the researchers write that the association may be bidirectional, as with sleep disturbances, so that neurological changes affecting cognition may also lead to more daytime napping.

Another tangle is nighttime sleep. Napping may compensate for poor sleep at night, but napping can also disrupt that sleep. To address this, the team adjusted for nighttime sleep duration, daytime sleepiness, and sleep apnea risk. Frequent napping, unintentional napping, and naps of 30 minutes or less remained significantly associated with dementia risk even after those adjustments.

Earlier research on napping and cognitive health in older adults has been mixed, with some studies finding elevated risk and others finding little evidence of a link. The authors call for future studies to disentangle the possible two-way relationship they describe.

The stakes are considerable: dementia is projected to double in the US by 2060. The researchers write that daytime napping might be a modifiable risk factor for prevention if further causal evidence supports it. Even if the link is not causal, they say, napping may serve as a marker of future dementia risk to guide prevention studies in high-risk groups. For now, the open question is which direction the relationship runs.