Sleep Disturbances and Dementia Risk in Older Adults: Findings From 10 Years of National U.S. Prospective Data.

INTRODUCTION: Previous research has identified a link between sleep disturbances and cognitive impairment; however, no study has examined this relationship using a national United States sample. This study examines how multiple longitudinal measures of sleep disturbances (sleep-initiation insomnia, sleep-maintenance insomnia, sleep-medication usage) are associated with dementia risk. METHODS: Ten annual waves (2011-2020) of prospective cohort data from a nationally representative U.S. sample of adults aged ≥65 years were analyzed from the National Health and Aging Trends Study. Sleep disturbances were converted into a longitudinal score and measured as sleep-initiation insomnia (trouble falling asleep in 30 minutes), sleep-maintenance insomnia (trouble falling asleep after waking up early), and sleep-medication usage (taking medication to help sleep). Cox regression models analyzed time to dementia diagnosis for a sample of 6,284 respondents. RESULTS: In the unadjusted model, sleep-initiation insomnia was significantly associated with a 51% increased dementia risk (hazard ratio=1.51, 95% CI=1.19, 1.90). Adjusted for sociodemographics, sleep-medication usage was significantly associated with a 30% increased dementia risk (adjusted hazard ratio=1.30, 95% CI=1.08-1.56). Adjusted for sociodemographics and health, sleep-maintenance insomnia was significantly associated with a 40% decreased dementia risk (adjusted hazard ratio=0.60, 95% CI=0.46, 0.77). CONCLUSIONS: These findings suggest that sleep-initiation insomnia and sleep-medication usage may elevate dementia risk. On the basis of the current evidence, sleep disturbances should be considered when assessing the risk profile for dementia. Future research is needed to examine other sleep disturbance measures and to explore the mechanisms for decreased dementia risk among older adults with sleep-maintenance insomnia.