0225 Actigraphy-Assessed Daytime Napping Links to Mild Cognitive Impairment and Dementia in Middle-to-Older Aged Adults

Abstract Introduction Prior studies of older adults have demonstrated that the development and progression of Alzheimer’s disease are tightly linked with longer daytime naps in a potentially bidirectional manner. It remains unclear whether daytime sleep behaviors in middle-to-older aged adults are linked to the risk for dementia. Methods We studied 85,037 cognitively intact non-shift-workers (baseline age=63 years, SD=8, range: 43-69; 57% female) in the UK Biobank cohort who completed 7-day actigraphy and had been followed for up to 8 years. We implemented the Cole-Kripke algorithm to identify daytime sleep episodes and considered three types of napping metrics: (1) mean nap duration between 9am-7pm; (2) intra-individual variability (individual SD) in the nap duration between 9am-7pm; (3) timing of napping quantified as the percentage of nap duration in each 2-h bin between 9am-7pm (9-11am, 11am-1pm, 1-3pm, 3-5pm, 5-7pm). Incidences of all-cause dementia and mild cognitive impairment (MCI) were identified via ICD-10 codes. Nap variables were square-root transformed to correct for skewness. We conducted Cox proportional hazards models, adjusting for demographic characteristics, lifestyle, comorbidities, polygenic genetic risk score for Alzheimer's disease, nighttime sleep, and chronotype. Results Almost all participants (99.97%) napped at least once. Median nap duration was 0.40 hours per day (IQR=0.20-0.78), and intra-individual variability of nap duration was 0.39 (IQR=0.19-0.69) hours. Twenty-eight percent (IQR=12%-52%) of the naps were taken between 9-11am, 5% (IQR=0%-17%) between 11am-1pm, 9% (IQR=0%-22%) between 1-3pm, 16% (IQR=1%-29%) between 3-5pm, and 17% (IQR=4%-32%) between 5-7pm. During follow-up, 557 (0.66%) participants developed MCI or dementia on average 4.62 (range: 0.01-7.98) years after baseline. Longer nap duration (for 1-SD, HR=1.21, 95%CI: 1.12-1.31, p< 0.0001), larger intra-individual variability (for 1-SD, HR=1.14, 95%CI: 1.04-1.24, p=0.004), and higher percentage of naps between 1-3pm (for 1-SD, HR=1.11, 95%CI: 1.02-1.22, p=0.017) were associated with increased risk for MCI/dementia. Conclusion Longer and increased intra-individual variability in daytime nap as well as higher percentage of naps in the early afternoon are associated with a greater risk of MCI/dementia in middle-to-older aged adults. These findings highlight the potential importance of monitoring napping in screening for the risk for developing dementia. Support (if any) AASM (290-FP-22), Alzheimer’s Association (AARFD-22-928372), NIH 5T32HL007901-25, BRI Fund to Sustain Research Excellence.