Objectively Measured Daytime Napping Patterns and All-Cause Mortality in Older Adults.

Importance: Daytime napping is common among older adults, but evidence linking objective daytime nap patterns to mortality is limited, as prior studies relied largely on self-report. Some daytime nap characteristics, such as timing and variability of nap duration across days, are also understudied. Objective: To test whether actigraphy-measured daytime nap duration, frequency, variability, and timing are associated with all-cause mortality. Design, Setting, and Participants: This prospective cohort study used data from the population-based Rush Memory and Aging Project, in which the analytic baseline was initiated in August 2005. Participants in this current study were community-dwelling adults aged 56 years or older in northern Illinois, with up to 19 years of follow-up. Data for this study were gathered until April 2025. Main Outcome and Measures: Daytime napping, defined as sleeping between 9 am and 7 pm and assessed by up to 14 days of actigraphy data. Cox proportional hazards regression models were used to estimate associations between baseline daytime nap characteristics (duration, frequency, variability in duration across days, and timing) and subsequent all-cause mortality. Results: Among 1338 participants over a mean (SD) follow-up of 8.30 (4.78) years (mean [SD] participant age, 81.40 [7.39] years; 1018 [76.0%] female), 926 (69.2%) died at a mean (SD) of 7.54 (4.52) years (range, 0.08-19.08 years) after analytic baseline. Participants wore the actigraphy device for a mean (SD) of 9.58 (1.22) days. After adjusting for all covariates, longer daytime nap duration (adjusted hazard ratio [AHR] per 1-hour increase, 1.13; 95% CI, 1.04-1.23; P = .005) and higher nap frequency (AHR per additional daily nap, 1.07; 95% CI, 1.02-1.13; P = .003) at baseline were associated with increased mortality. Morning nappers had higher mortality risk compared with early afternoon nappers (AHR, 1.30; 95% CI, 1.03-1.64; P = .03). Variability in daytime nap duration was not associated with mortality after covariate adjustment (AHR per 1-hour increase, 1.01; 95% CI, 0.89-1.14; P = .93). Conclusions and Relevance: In this prospective cohort study of community-dwelling older adults, longer and more frequent daytime napping, especially in the morning, were associated with higher all-cause mortality. The findings suggest incorporating wearable device-based daytime nap assessments into clinical and public health practices may provide novel opportunities for early risk identification of health conditions.