A recent multiyear study has found that older adults who sleep a moderate amount exhibit less cognitive decline compared to those who sleep either too little or too much. The research indicates that both short and long sleep durations are associated with greater cognitive impairment, even after accounting for early Alzheimer’s disease factors.
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The study, published in the journal *Brain*, tracked cognitive function over several years in a significant cohort of older adults. Researchers analyzed their cognitive performance alongside levels of Alzheimer’s-related proteins and brain activity during sleep, providing essential insights into the complex interplay between sleep, Alzheimer’s, and cognitive health.
Brendan Lucey, the first author and an associate professor at Washington University School of Medicine in St. Louis, emphasized the importance of identifying a “sweet spot” for sleep duration, saying that cognitive performance appeared stable within a specific range. Participants sleeping fewer than 4.5 hours or more than 6.5 hours per night showed declines in cognitive scores, while those in the middle range—approximately 5.5 to 7.5 hours as estimated from EEG recordings—maintained stable performance.
The study included 100 participants, mostly aged 75, who provided both blood and cerebrospinal fluid samples for analysis of Alzheimer’s proteins. The relationship between sleep duration and cognitive decline was also observed for specific sleep phases, including REM and non-REM sleep, and persisted when adjusting for various confounding factors like age, sex, and genetic risk factors such as the APOE4 variant.
David Holtzman, a co-senior author and neurology professor, pointed out the notable finding that both insufficient and excessive sleep can lead to cognitive decline, suggesting that sleep quality might be more crucial than total sleep duration.
While individual sleep needs vary, Lucey recommends that those struggling with sleep should seek treatment, as improved sleep can positively affect cognitive performance. Co-senior author Beau M. Ances noted that physicians should inquire about sleep quality in patients presenting cognitive concerns, highlighting sleep as a potentially modifiable factor in cognitive health.
The study received support from the National Institutes of Health (NIH), the American Sleep Medicine Foundation, the Roger and Paula Riney Fund, and the Daniel J. Brennan, MD Fund.