Seniors who napped most days had a 48% higher dementia rate in a study of 995 Medicare enrollees

Older adults who napped every day or most days developed possible or probable dementia at a rate 48% higher than people who rarely or never napped, according to a Johns Hopkins analysis of 995 Medicare beneficiaries. Every participant was free of dementia in 2013, when napping habits were recorded, and they were followed through 2023. The authors stop short of saying the naps caused anything.

AI, explained every day: The Deep View is the go-to daily newsletter for 600,000+ founders, knowledge workers and professionals who want to stay up to date with artificial intelligence.

Get The Deep View →

We may earn a commission if you sign up.

Adam Spira, a psychologist and sleep researcher at the Johns Hopkins Bloomberg School of Public Health, is the senior author. Kening Jiang, a postdoctoral fellow, is first author on the paper, and the author list runs to 13 names, with Alden Gross, Emerson Wickwire, Atul Malhotra and Christopher Kaufmann among the co-authors. The question they asked is whether daytime napping tracks dementia risk independently of how well people sleep at night, which earlier studies had left unclear.

Frequent, unintentional and short naps in the 995-person sample

The data come from the National Health and Aging Trends Study, known as NHATS, a nationally representative survey of Medicare beneficiaries aged 65 and older. Johns Hopkins runs it, Westat collects the data and the National Institute on Aging funds it. The napping analysis, published in The Journals of Gerontology, Series A, sorted the 995 participants by how often they napped, whether the naps were intentional, and whether they lasted 30 minutes or less.

The journal abstract reports a hazard ratio of 1.48 for frequent nappers, with a 95% confidence interval of 1.14 to 1.94. Unintentional napping carried a hazard ratio of 1.39, a 39% higher rate, and naps of 30 minutes or less a ratio of 1.40, or 40% higher. Of the 995 participants, 417, or 41.9%, developed possible or probable dementia over a median follow-up of about five years.

A hazard ratio of 1.48 describes a relative rate over the follow-up window, not an absolute chance of developing dementia. It says that among comparable participants, those who napped daily or most days were diagnosed at about one and a half times the pace of rare nappers. With 417 diagnoses spread across 995 people, the study has enough events to produce a stable estimate, though the interval from 1.14 to 1.94 shows the true figure could sit well above or below 48%.

Infrequent napping and intentional napping showed no significant association once the models were adjusted. Longer naps pointed in the same direction, but the ratio of 1.28 had an interval running from 0.96 to 1.69, which includes no effect.

Adjustments for nighttime sleep, apnea risk and sleepiness

A plausible objection is that people who nap a lot simply sleep badly at night. The models accounted for that. According to ScienceAlert’s account, the researchers adjusted for age, sex, race and ethnicity, education, smoking, body mass index and health conditions, along with nighttime sleep duration, daytime sleepiness and sleep apnea risk. The 48% gap survived those controls.

Frequent, unintentional and short naps were also linked to memory impairment during follow-up, a second signal pointing the same way as the dementia diagnoses. Naps taken on purpose were the group with the least evidence of trouble, which suggests the kind of nap may matter as much as the count. Napping was self-reported by participants in 2013 interviews, and the analysis separated people who dozed off without meaning to from those who chose to lie down, a distinction the authors found informative because only the unplanned kind carried a significant signal.

What an observational design cannot settle

Spira said in the university’s news release that more frequent napping could be a marker of changes in the brain. Jiang added that monitoring napping behavior could serve as an early and accessible marker. Both statements describe napping as a signal to watch, which is a narrower claim than napping as a hazard to avoid.

The paper itself says the association between napping and dementia may be bidirectional. Daytime naps could compensate for poor nighttime sleep, napping could disrupt nighttime sleep, or early, undiagnosed brain changes could make people sleepier by day and show up as dementia years later. NHATS recorded napping once, in 2013, so the study cannot tell whether habits shifted as the disease developed. Dementia was classified as possible or probable rather than confirmed by clinical workup, which is standard for a large survey but leaves some room for misclassification at the edges.

The authors conclude that daytime napping may be a modifiable risk factor for dementia if further evidence supports it, and at minimum a useful marker of future dementia risk. They call for studies with more detailed napping measures and longer follow-up to disentangle the two. Earlier research has produced mixed results. Funding came from National Institute on Aging grants, and the open question is whether any trial can test a cause by changing how older adults nap.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

AI, explained every day: Get The Deep View →

We may earn a commission if you sign up.