Frequent or Unintended Daytime Naps May Signal Higher Dementia Risk in Older Adults, Johns Hopkins Study Finds

BALTIMORE — Older adults who nap frequently, fall asleep during the day without meaning to or take short naps may face a higher risk of developing dementia, according to a new study by researchers at the Johns Hopkins Bloomberg School of Public Health.

The study, published in The Journals of Gerontology: Medical Sciences, suggests that daytime napping habits could serve as an early warning sign that helps doctors identify people at greater risk of cognitive decline.

"Monitoring napping behaviors could serve as an early and accessible marker to help identify older adults at higher risk for dementia and guide targeted interventions for dementia prevention," lead researcher Kening Jiang, a postdoctoral fellow in mental health research at the Johns Hopkins Bloomberg School of Public Health, said in a news release.

A decade of data

The researchers analyzed data from 995 Medicare beneficiaries ages 65 and older who took part in the National Health and Aging Trends Study, a long-running national survey of older Americans.

None of the participants had possible or probable dementia when researchers began tracking their napping habits in 2013. The team followed them through 2023, examining whether they developed dementia over the roughly 10-year period.

Researchers compared how often participants napped, whether their naps were intentional or unintentional and how long they typically slept during the day.

Key findings

Compared with people who did not nap, frequent nappers, those who napped most days or every day, had a 48% higher risk of developing possible or probable dementia.

People who said they at least sometimes fell asleep during the day without intending to had a 39% higher risk.

Napping for 30 minutes or less was associated with a 40% higher risk of dementia after researchers accounted for other factors.

By the end of the study, about half of frequent nappers had developed signs of dementia, compared with roughly 38% of people who did not nap, according to a summary of the findings by StudyFinds.

The researchers found no association between dementia risk and infrequent napping or naps that were taken intentionally.

Cause or warning sign?

The researchers stressed that the study was observational and does not prove that napping causes dementia.

Jiang told Newsweek that "whether daytime napping causes dementia has not yet been established," and that more research is needed to determine whether the relationship is causal.

The link could run in either direction. Napping may be a risk factor for dementia, but the early stages of dementia could also affect parts of the brain that regulate wakefulness, leading people to nap more often.

Study author Adam Spira, a professor of mental health at Johns Hopkins, has suggested that one possible explanation is that daytime napping may interfere with nighttime sleep. Poor nighttime sleep has been linked in other research to cognitive decline and to the buildup of proteins associated with Alzheimer's disease.

Some research has also suggested that a brain affected by dementia may struggle to clear waste effectively during sleep.

Why short naps stood out

The finding that shorter naps were associated with higher risk may seem surprising, since brief naps are often recommended as a healthy way to recharge.

Researchers noted that the link between longer naps and dementia risk weakened once nighttime sleep factors were taken into account, suggesting that the overall pattern of a person's sleep may matter more than any single nap.

Implications for doctors and families

The researchers said their findings highlight the importance of considering daytime napping, in addition to nighttime sleep, when assessing older adults' health.

Because napping habits are easy to observe and report, they could provide a simple, low-cost way to flag people who may benefit from further cognitive screening.

Frequent unintentional dozing during the day can also be a sign of other health problems, such as obstructive sleep apnea, depression or side effects from medications, which may be treatable.

Experts generally advise older adults who notice a significant change in their sleep or napping patterns to talk with a health care provider.

Growing concern

Dementia affects millions of Americans, and the number is expected to rise as the population ages. There is currently no cure, making early identification of risk factors a major focus of research.

Previous studies have linked poor sleep, sleep disorders and excessive daytime sleepiness to a higher risk of cognitive decline. The new study adds to evidence that daytime sleep patterns may be an important part of that picture.

Limitations

The study relied on participants' own reports of their napping habits, which may not always be accurate. The researchers also noted that their findings need to be confirmed in further studies with more detailed information about napping and longer follow-up.

The study concluded that daytime napping may be a modifiable risk factor for dementia if supported by further evidence.

Researchers said future studies should examine whether changing napping habits or improving nighttime sleep could help lower dementia risk.

For now, the findings suggest that frequent or unexpected daytime sleepiness in older adults may be worth paying attention to as a possible early signal of changes in brain health.