Frequent daytime naps among older adults are linked to a significantly higher risk of dementia, according to a Johns Hopkins University study.
The research followed 995 Medicare beneficiaries in the United States who were aged 65 and older and showed no signs of cognitive impairment when the project began in 2013. Over a ten-year observation period, participants who napped daily or almost daily faced a 48 percent higher risk of developing dementia compared with individuals who rarely or never napped during the day.
The heightened risk persisted even after researchers adjusted for demographic factors, general health conditions, and specific nocturnal sleep characteristics, such as nighttime sleep duration, daytime sleepiness, and the risk of obstructive sleep apnea.
The intention and duration of the naps also showed clear patterns. Participants who took unintentional naps, drifting off without planning to sleep, had a 39 percent higher risk of developing dementia. In addition, taking short naps lasting 30 minutes or less was linked to a 40 percent higher risk compared with not napping.
Brain changes and nap habits
Adam Spira, a professor in the Department of Mental Health at the Johns Hopkins Bloomberg School of Public Health and the senior author of the paper, explained the biological context behind the findings.
Spira said more frequent napping might be a marker of underlying changes in the brain, rather than a direct cause of the brain changes that lead to dementia.
The investigators pointed to a likely bidirectional relationship between daytime resting habits and cognitive decline. Frequent napping may act as a potential risk factor for dementia, while the deterioration of brain regions responsible for regulating wakefulness, an event that can occur early in the course of dementia, may also prompt older adults to take more frequent daytime naps.
To verify that undiagnosed cases of dementia were not distorting the results, the scientists conducted an analysis that excluded all diagnoses made within the first five years of the study. Even with those initial five years omitted from the data, the observed connections between dementia and both frequent and unintentional napping remained similar.
The authors stressed that the results are observational and cannot prove that napping causes dementia. They concluded that long-term studies are needed to determine how napping habits interact with dementia risk, and whether changing daytime rest patterns could help delay or prevent the onset of the condition.
Dementia symptoms and Alzheimer's disease
Dementia is a clinical syndrome involving the progressive deterioration of cognitive functions, including memory, thinking, language, judgment, and orientation. The loss of these mental abilities gradually undermines a person's independence and impairs their ability to carry out daily tasks.
Alzheimer's disease is the most common form of dementia, representing between 60 percent and 80 percent of all diagnosed cases. The condition is marked by the buildup of abnormal proteins in the brain, which progressively destroy nerve cells and disrupt communication between neurons.
Other health events, including severe physical trauma, specific infections, thyroid disorders, and vitamin deficiencies, can also cause dementia symptoms, though such cases are less frequent and some can be treated or reversed. Advancing age, genetics, and family medical history remain the primary factors determining whether an individual develops dementia.
Sleep plays a critical role in brain health, with medical specialists noting that poor or disrupted rest can prevent the brain from clearing out toxic proteins that accumulate during waking hours. The Johns Hopkins research indicates that daytime sleep habits may offer important clues regarding these neurological mechanisms.
Study methodology and Medicare data
The findings were published on October 5, 2026, in The Journal of Gerontology: Medical Sciences, a peer-reviewed academic publication focused on the medical aspects of aging.
Scientists conducted the investigation at the Johns Hopkins Bloomberg School of Public Health. Located in Baltimore, Maryland, Johns Hopkins is one of the leading private research institutions in the United States and was founded as the nation's first dedicated research university.
The research team tracked participants over ten years using records from the National Health and Aging Trends Study, a nationally representative survey of older American adults. The dataset focused on beneficiaries of Medicare, the federal health insurance programme for individuals aged 65 and older, evaluating how self-reported nap frequency, intentionality, and length correlated with cognitive outcomes over a decade.
Global research on rest and daylight exposure
The Johns Hopkins study is part of a broader body of international research investigating how sleep routines and environmental factors correlate with cognitive decline.
In the United Kingdom, researchers at the University of York recently evaluated the resting patterns of 4.5 million people to determine the specific circumstances under which the risk of developing dementia increases.
In another study, researchers at Guangzhou Medical University in China assessed data from nearly 88,000 individuals. That investigation linked spending limited time in natural daylight with a greater risk of dementia, suggesting that broader circadian rhythms across day and night may influence cognitive preservation.
Cultural attitudes and physical benefits of napping
The association between napping and dementia stands in sharp contrast to traditional attitudes toward the practice, which has long been viewed as beneficial for both mind and body.
In Spain, taking a midday siesta is deeply ingrained in national culture and social life. Surveys suggest that between 16 percent and 18 percent of Spaniards nap on a regular basis, while roughly 22 percent take naps occasionally, particularly on weekends.
Yet despite that reputation, about 60 percent of people in Spain never or almost never nap. Regular afternoon rest is particularly uncommon in regions such as Galicia, Catalonia, and Madrid, where busy work schedules and modern lifestyles leave little opportunity for an afternoon pause.
Under ordinary circumstances, medical experts agree that a short nap lasting roughly 30 minutes offers notable physical and mental advantages. A brief rest can restore energy, improve productivity, help consolidate newly learned information, relieve stress, reduce blood pressure, and lift mood.
The study authors reiterated that people who take an occasional midday nap to recharge should not feel alarmed, as the observational research does not demonstrate that daytime sleep damages brain tissue. Instead, researchers view sudden or frequent increases in unintentional daytime sleeping as a possible clinical marker that may warrant closer observation by medical professionals.
