Falling asleep in your armchair in the middle of the afternoon is one of the simple pleasures of life.
But depending on how often you do it, those daytime naps could be a warning sign of worsening cognitive health, research suggests.
In a new study, researchers found that older adults who nap frequently were significantly more likely to develop dementia over the next decade, compared to people who rarely or never nap.
The results, published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciencesdo not mean that napping causes cognitive decline, but they do identify napping as a risk factor for dementia that we should pay more attention to.
“More frequent naps might be a marker of changes in the brain, rather than a cause of brain changes leading to dementia,” says psychologist and sleep researcher Adam Spira of Johns Hopkins University.
In their study, Spira and fellow researchers analyzed data from the National Health and Aging Trends Study (NHATS), a longitudinal survey of U.S. Medicare beneficiaries aged 65 and older.
The team looked at data from 995 NHATS participants, all of whom answered questions about their napping habits as part of the research, and none of whom had probable or possible dementia at the start of the study.
Over a median follow-up period of five years, 417 (41.9 percent) of participants were classified as having developed possible or probable dementia since the start of the study.
After adjusting for a series of potential confounders in the data — including age, gender, race/ethnicity, education, smoking status, body mass index, and various health conditions and sleep factors — the researchers found that frequent naps had the highest risk of developing the disease, compared to infrequent naps and no naps.
Frequent napping people – people who reported taking a nap every day or almost every day – had a 48% higher rate of dementia than people who never or rarely took a nap.
Involuntary naps were also associated with a higher risk of dementia (39% higher rate than non-naps).
The length of naps was also a factor, with people who napped for 30 minutes or less having a 40% higher rate of dementia than people who didn’t nap during the study period.
Frequent, involuntary, shorter naps (30 minutes or less) were also found to be associated with higher risks of developing memory problems during follow-up, the researchers found.
Of note, researchers also found signs of elevated dementia risk associated with infrequent napping, intentional napping, and napping for periods of 30 minutes or more, but the effects were not statistically significant after adjustment in the final analysis.
Other studies have previously explored the relationship between napping and cognitive health in older adults, but results have been mixed, with some studies showing signs of elevated cognitive risks associated with napping, and others finding little evidence of a link.
Due to the observational nature of the new study, the results cannot be interpreted as evidence that frequent, involuntary or short naps cause dementia, and the researchers acknowledge that the links they found are complicated.
“As with sleep disorders, the association between napping and dementia may be bidirectional,” they write in their paper, “so that neurological changes that negatively affect cognitive function may also lead to increased daytime napping.”
In other words, if older adults start taking a lot of naps during the day, that could be a sign of worsening brain health — but that worsening brain health could also make them sleepier, prompting them to doze off during waking hours.
Another complicating factor is that daytime napping may be a compensatory mechanism, compensating for sleep disturbances at night. But just as poor nighttime rest can lead to make-up naps during the day, a nap can also disrupt nighttime sleep.
In the study, researchers explained this by adjusting for other sleep-related factors (nighttime sleep duration, daytime sleepiness, and risk of sleep apnea), and the results suggest that frequent naps, involuntary naps, and naps lasting 30 minutes or less remained significantly associated with increased dementia risk, even after accounting for these other sleep characteristics.
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The researchers call for future studies to “unravel” the possible bidirectionality of the nap-dementia association they demonstrated here.
Although we don’t fully understand the nature of this link, we hope that new research can solve the puzzle, which could lead to new ways to combat dementia, a disease expected to double in the United States by 2060.
“Daytime napping could be another modifiable risk factor to target in older adults for primary prevention of dementia, if supported by other causal evidence,” the researchers write.
“Even if this association is not causal, napping may be a useful marker of future dementia risk to guide subsequent prevention studies among high-risk populations.”
The results are reported in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we are proud of our process, we are only human. If you spot an error, please let us know.
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