A common daytime habit many older adults do could be increasing their risk of developing dementia, a new study has found.
Researchers at Johns Hopkins University said that daytime napping, specifically how often, how intentionally and how long, was found to influence a person's risk of developing dementia.
However, the experts emphasized that the findings were observational and do not establish that napping directly causes dementia. The study was published online in The Journals of Gerontology: Medical Sciences on October 5.
These findings follow on from previous research in the field, some of which has indicated that sleepiness has been associated with an abnormal accumulation of proteins associated with dementia in the brains of otherwise healthy adults, Dr. Andrew Varga, a sleep neurologist and neuroscientist at the Icahn School of Medicine at Mount Sinai, told Newsweek.
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Daytime Napping Influenced Dementia Risk
The researchers reviewed the clinical data of almost 1,000 U.S. Medicare users who were at least 65 years old and who did not have dementia at the start of the study in 2013. They tracked the participants for up to 10 years.
They found that those who napped frequently, meaning either most days or every day, had a 48 percent higher risk of developing dementia compared to those who either rarely or never napped.
The researchers said this was the case even after several demographic factors were accounted for, such as health conditions and nighttime sleep characteristics.
Unintentional napping, so falling asleep without intending to, was linked to a 39 percent higher risk of developing dementia as well.
They also identified that duration of the nap had an impact too. Daytime sleeping for 30 minutes or less was associated with a 40 percent higher risk.
A 'Two-Way' Association
The scientists noted that there could be a "two-way" nature to the association, meaning that cognitive decline can cause more frequent intentional and unintentional napping, as well as napping potentially increasing risk of the disease.
Varga said that as the proteins amyloid and tau – which are associated with dementia development – "start to accumulate and neurons start to become dysfunctional or die, some of the earliest neurons affected are ones that control the regulation of sleep and wake as well as the circadian rhythm."
"So, this means that periods of sleep can come on during the day at inappropriate times," he said.
However, as the researchers followed some participants for 10 years, who did not have dementia at the start of the study, they said that the findings seem to suggest that napping pattern could have an influence on dementia development, and not just be a reflection of the disease.
How Could Napping Affect Dementia Risk?
In terms of how napping could affect dementia risk, Adam Spira, the study author and a professor of mental health at Johns Hopkins University, told Newsweek that one possibility is daytime napping may affect nighttime sleep.
"This matters because disturbed nighttime sleep is linked to brain changes associated with dementia, such as the accumulation of proteins like beta-amyloid and increased neuroinflammation," he said.
He said, specifically, "napping may reduce 'homeostatic sleep drive,' the body's natural drive for sleep that builds up throughout the day, potentially disrupting nighttime sleep."
Both sleep deprivation and sleep apnea have been "shown to raise risk for dementia, with proposed mechanisms including increased production of amyloid and tau (the bad proteins that accumulate in Alzheimer's disease), decreased clearance of amyloid and tau from the brain, increased inflammation, and altered immune function," Varga said.
Dr Omonigho Bubu, the director of the Aging Research in Sleep Equity and Dementia Prevention program at New York University, told Newsweek that daytime napping may also reflect "underlying sleep disruption, excessive daytime sleepiness, or early neurodegenerative changes already affecting the brain systems that regulate sleep and wakefulness."
"In that sense, napping may be either a contributing factor, an early warning sign, or both," he said.
What The Findings Mean
Kening Jiang, the study's first author and postdoctoral fellow at Johns Hopkins University, told Newsweek the findings suggest daytime napping "may be an important potential risk factor for dementia," and "highlight the importance of considering daytime napping, in addition to nighttime sleep, as napping behaviors may help identify older adults at higher risk of dementia and inform dementia-prevention strategies."
"However, whether daytime napping causes dementia has not yet been established, and more research is needed to understand whether this is a causal relationship," he said.
Varga said that it's important to note "not all napping is bad, and there are documented benefits of napping," but it becomes a worry when "the napping is in response to either insufficient nighttime sleep or, sleep that is of sufficient duration but is interrupted by some disorder."
Bubu said the findings suggest that "daytime sleep behaviors should not be overlooked in older adults." He added that "the key message is not that all napping is harmful, but that changes in napping patterns deserve attention."
Reference
Kening Jiang, Alden L Gross, Catriona Tingsea Wu, Junxin Li, Halima Amjad, Emerson M Wickwire, Jennifer S Albrecht, Atul Malhotra, Chien-Yu (Irene) Tseng, Marc Kaizi-Lutu, Chunyu Liu, Christopher N Kaufmann, Adam P Spira, (2026) Napping characteristics and incident dementia: results from the National Health and Aging Trends Study, The Journals of Gerontology: Series A. https://doi.org/10.1093/gerona/glag208
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Contact Newsweek editors on this story: Kara Dolman and Paul Donnelley.