Older adults who napped on most days were more likely to develop dementia over the next decade than those who rarely napped, a new study from Johns Hopkins researchers reports. Over up to 10 years of follow-up, people who napped most days or every day had a 48% higher risk of dementia than people who rarely or never napped1. Falling asleep during the day without meaning to was tied to a 39% higher risk1.
The researchers stress that this is a link, not proof of cause. They suggest that more frequent daytime napping may be an early sign of changes already under way in the brain2.
What the researchers did
The team used data from the National Health and Aging Trends Study, a national survey of people on Medicare, the U.S. health program for older adults2. In 2013, 995 Americans aged 65 and older answered questions about their sleep. None of them had dementia at the time2. The researchers then followed them for about ten years, until 20232.
Participants described their own napping habits: how often they napped, how long the naps lasted, and whether the nap was planned or happened by accident1. “Frequent” meant napping on most days or every day3.
The study was led by Kening Jiang, a postdoctoral fellow in the Department of Mental Health at the Johns Hopkins Bloomberg School of Public Health1, with Adam Spira, a professor at the school, as senior author23. It was published in The Journal of Gerontology: Medical Sciences1.
The numbers so far
Compared with people who rarely or never napped, the study reported these differences in dementia risk14:
- Napping most days or every day: 48% higher risk.
- Falling asleep without meaning to: 39% higher risk.
- Naps of 30 minutes or less: 40% higher risk.
These links held after the researchers accounted for how long people slept at night, how sleepy they felt during the day, and signs of sleep apnea, a condition in which breathing stops and starts during sleep23. Infrequent naps and planned naps showed no significant link2. For naps longer than 30 minutes, the link was weaker once nighttime sleep patterns were taken into account3.
“Our study highlights the importance of looking beyond just how long people nap and considering other napping characteristics, such as how frequently they nap and whether their naps are intentional,” Spira and Jiang told Fox News Digital3.
A pattern that showed up years before diagnosis
One worry with studies like this is that people in the very early stages of dementia might already be napping more, which could make naps look like a cause when they are really a symptom. To check this, the team re-ran the analysis after removing everyone who was diagnosed with dementia in the first five years3. The links with frequent and unintentional napping did not change2, which the researchers read as a sign that changes in napping habits can appear years before a formal diagnosis3.
Spira put it this way:
“More frequent napping could be a marker of changes in the brain rather than a cause of brain changes that lead to dementia.”
He was quoted by Futura-Sciences2. Jiang said that “monitoring napping behaviors could serve as an early and accessible marker” to help identify older adults at higher risk2.
Why naps and dementia might be connected
Jiang told Medical News Today that the reasons are not yet fully understood1. She described several possibilities:
- Disturbed night sleep. Napping in the day may reduce the drive to sleep at night, which could lead to sleep problems at night that have also been linked to dementia risk1.
- Inflammation. Other pathways, such as inflammation, may also play a role1.
- The disease itself. More daytime napping may reflect early brain damage that affects how the body controls sleeping and waking1.
The researchers noted that brain regions that help keep people awake can start to break down in the early stages of dementia, which could lead to more daytime tiredness3. Health Chosun described the team’s view as a possible two-way relationship between napping and dementia4.
Dung Trinh, an internist with MemorialCare Medical Group who was not involved in the study, told Medical News Today: “It is important to emphasize that this does not mean napping causes dementia. Rather, changes in daytime sleeping patterns may be an early warning sign of underlying changes in the brain, potentially before more obvious memory symptoms appear.”1
What the study does not show
This was an observational study: researchers watched what happened to people without changing anything about their lives. It shows that napping habits and dementia go together, not that one causes the other2. “We did not directly intervene on participants’ napping behaviors to examine whether changing these behaviors would affect their dementia risk,” Spira and Jiang said3.
Other limits reported in coverage of the study:
- Napping was self-reported in a survey, not measured with a device2.
- Dementia was identified using a validated algorithm, a scoring method based on survey data, rather than a clinical diagnosis for every participant2.
- Earlier studies on napping and brain health have reached mixed conclusions2.
- With just under 1,000 people, the study is modest in size. Health Chosun noted that larger, long-term studies are needed to clarify the relationship4.
The percentages are relative risks. They describe how much more often dementia appeared in one group than another, not the chance that any one person who naps will develop it. The sources do not report how many people in each group were diagnosed.
Who is behind it
The study was carried out at the Johns Hopkins Bloomberg School of Public Health and funded by the National Institute on Aging, a U.S. government research agency2. It drew on the National Health and Aging Trends Study, a national survey rather than a company-run program2. The sources do not report any company funding or commercial ties.
How it fits the field and what to watch next
Dementia researchers have increasingly looked at factors in daily life that might be changed. Past studies report that 42% of adults over 55 will develop dementia, and earlier research has pointed to diet, physical activity, staying mentally and socially engaged, and enough nighttime sleep as possible ways to lower risk1. “Growing evidence suggests that many cases of dementia may be preventable by addressing modifiable risk factors. However, dementia is multifactorial, and much remains to be understood about how different factors contribute to dementia risk,” Jiang said1.
The research team said looking at daytime napping alongside nighttime sleep gives a clearer picture than nighttime sleep alone3. Jiang named the next step: “An important next step is to generate stronger evidence about whether the relationship between daytime napping and dementia is causal, particularly whether changing napping behaviors could help reduce dementia risk among older adults.”1 She also said it is important to better understand the mechanisms behind the link1.
Things to watch include studies that measure sleep with devices rather than surveys, larger groups followed over longer periods, and any trial that tests whether changing nap habits affects later brain health. Until then, the researchers’ own summary stands: “Although we don’t know whether napping causes dementia, our study findings suggest that daytime napping patterns may be useful indicators of future dementia risk.”3
