This Common Daytime Habit May Be Linked To A Higher Dementia Risk, Study Finds

Researchers at Johns Hopkins' Bloomberg School of Public Health followed just under 1,000 adults aged 65 and older for 10 years and found that people who napped every day or nearly every day had a 48% increased risk of developing dementia compared with those who rarely or never napped. The study, published in the Journal of Gerontology: Medical Sciences, began with participants who had no dementia, and their napping habits were self-reported.

People who napped for less than 30 minutes had a 40% higher risk of dementia, and those who napped unintentionally had a 39% higher risk. Unintentional napping was defined as falling asleep without meaning to, such as dozing off on a couch while reading. Roughly a quarter of participants reported frequently napping unintentionally, meaning most older adults in the study did not doze off without meaning to.

The findings do not mean all napping is harmful. Adam Spira, the study's senior author, said in a press release that "More frequent napping could be a marker of changes in the brain, rather than a cause of brain changes that lead to dementia." Dr. Heather Elizabeth Whitson, director of the Duke Center for the Study of Aging and Human Development in North Carolina, who was not affiliated with the research, said: "Would interrupting that behavior be protective against dementia? We definitely cannot conclude that from the study."

Whitson said the data suggest the most problematic pattern is unintentional naps of short duration, while intentional, longer naps did not seem as negative. A planned snooze after a late night or early morning can be helpful, and she said an hour-long nap the next day after a disturbed night's sleep is fine. Dr. Mario Dulay, a neuropsychologist at Houston Methodist who was also not affiliated with the research, said 45 minutes is a good goal because it takes about that long to get through a whole sleep cycle, including REM sleep and all stages of sleep. Whitson added that habitual siestas tied to a cultural norm are "probably not a problem either."

Other experts urged caution about the wider evidence. Dulay said researchers noted that "many studies find the opposite or find no results." The study also relies on participants' self-reports, which could leave room for misremembering how often or how long they napped. Whitson described the relationship between sleep and dementia as undeniable but complicated, pointing to a bidirectional link in which neurodegenerative changes can disrupt sleep and disrupted sleep can also be a risk factor for dementia.

Whitson said falling asleep unintentionally during the day is not a normal part of aging and is worth raising with a doctor, since it could be linked to dementia or to a treatable condition such as obstructive sleep apnea. She also noted that more than 190 randomized human protocols are underway testing interventions for diseases that cause dementia, and said a diagnosis is better than uncertainty because it lets families and care teams plan treatments and safety measures.