Early morning naps are correlated with incident Alzheimer’s Dementia in older adults

Abstract

AbstractBackgroundPrevious findings suggest that frequent and longer naps during daytime are associated with elevated risks of Alzheimer’s dementia among older adults. This study aims to further examine whether naps during a particular time of a day are differentially linked to risk of Alzheimer’s dementia.MethodA total of 1,203 participants from the Rush Memory and Aging Project (mean age at actigraphy = 80.85±7.30 years; 77% female) wore accelerometers (Actical) for up to 14 (mean = 9.57±1.17) days and completed annual neurocognitive assessment for up to 17 (mean = 6.92±4.12) years. A validated algorithm was used to identify daytime naps between 9am and 7pm. We categorized participants into those who napped versus those who did not nap during each time period, i.e., morning (9‐11am), noon (11am‐1pm), early afternoon (1‐3pm), late afternoon (3‐5pm), and early evening (5‐7pm). We conducted Cox proportional hazards models to test whether napping at a specific time of day is correlated with incident Alzheimer’s dementia, adjusting for age, sex, education years, length of actigraphy recording, body mass index, intradaily variability of rest‐activity rhythms, and nighttime sleep duration.ResultAmong all participants, 357 developed Alzheimer’s dementia during follow‐up (mean time to incidents = 6.34±3.98 years). Compared to those who did not nap in the morning (9‐11am), participants who napped in the morning had 1.4‐fold (HR[95%CI] = 1.43 [1.07‐1.93], p = 0.01) risk for developing Alzheimer’s dementia. This association was attenuated after further adjusting for total nap duration and frequency (HR[95%CI] = 1.32[0.97‐1.79], p = 0.07). However, napping during other time periods was not associated with risk for Alzheimer’s dementia, after adjusting for the covariates (noon: HR[95%CI] = 1.26[0.94‐1.68], p = 0.12; early afternoon: HR[95%CI] = 1.22[0.81‐1.84], p = 0.33; late afternoon: HR[95%CI] = 1.22[0.81‐1.84], p = 0.34; early evening: HR[95%CI] = 0.84[0.62‐1.13], p = 0.24).ConclusionNapping in the morning may link to an increased risk of Alzheimer’s dementia in older adults. A potential explanation is that individuals who nap more in the morning are more likely to experience disturbances in sleep‐wake regulation. Future studies should investigate this underlying mechanism and test whether interventions to reduce morning naps or consolidate naps can benefit neurocognitive outcomes.