Two main findings from a long-term study suggest that daytime sleep exceeding one hour daily is linked to a higher dementia risk in older adults, with an estimated 40 percent increase observed in some analyses. This conclusion comes from a report citing results of research conducted by university researchers in California, and it has been referenced in the Chinese edition of the report. The study tracked 1401 volunteers for fourteen years, focusing on how sleep patterns relate to changes in cognitive abilities over time. During the study, daytime sleep duration tended to rise with age in about three quarters of participants who started with intact cognitive function, averaging roughly eleven minutes more sleep per year for those individuals. About six years into the study, around one-quarter of participants who began with normal cognition were later diagnosed with dementia. Taken together, these findings point to daytime sleepiness that is both frequent and prolonged as a potential contributor to dementia risk in otherwise healthy older adults. In this context, the message is not that sleep directly causes dementia, but that persistent daytime sleepiness may serve as an important signal associated with cognitive decline and warrants further clinical attention and lifestyle assessment.
