Older adults who nap most days or every day may face a notably higher risk of developing dementia, according to a decade-long study from the Johns Hopkins Bloomberg School of Public Health.
The research, published in The Journals of Gerontology: Series A, followed nearly 1,000 adults aged 65 and older to examine how daytime rest habits related to long-term brain health.
Participants who napped most days or daily showed a 48% higher dementia risk than those who rarely or never napped.
Unintentional daytime sleep was linked to a 39% higher risk, while nap duration also showed associations with dementia outcomes.
Duration and Frequency Both Matter
Naps lasting 30 minutes or less were associated with a 40% higher dementia risk, even after researchers adjusted for other health factors.
The relationship between longer naps and dementia was less pronounced once nighttime sleep patterns were taken into account.
Participants were initially enrolled in 2013, when they showed no signs of memory or thinking problems.
The associations held even after accounting for nighttime sleep duration, daytime drowsiness and indicators of sleep apnea.
Adam Spira, Ph. D.
, a professor at the Bloomberg School, and postdoctoral fellow Kening Jiang, Ph. D.
, said the findings support examining multiple characteristics of daytime naps rather than focusing solely on duration.
They stressed the importance of looking beyond how long people nap and considering how frequently they nap and whether the naps are intentional.
The researchers described the results as longitudinal evidence connecting frequent and unintentional napping with dementia risk, but the study does not establish that naps directly cause the condition.
Spira and Jiang noted that daytime rest and nighttime sleep may influence each other, potentially complicating the relationship between sleeping habits and brain health.
Napping may compensate for poor nighttime sleep, but it could also reduce the drive to sleep at night and contribute to nighttime sleep disturbances, another potential dementia risk factor.
The team suggested that changes in daytime alertness may reflect underlying neurological changes rather than cause them.
Brain regions responsible for regulating wakefulness can begin deteriorating in the early stages of dementia, potentially contributing to increased daytime fatigue.
To test whether the association might reflect dementia already developing, the researchers repeated the analysis after excluding participants diagnosed during the first five years.
The connection between frequent, unintentional naps and dementia remained similarly strong, suggesting altered napping patterns may emerge years before a formal diagnosis.
The authors emphasized that the research was observational and could not determine whether changing napping habits would alter dementia risk.
They said the findings identify daytime sleep patterns as a potential indicator of future dementia risk, while acknowledging that the relationship remains uncertain.
