Impact of heat exposure on sleep health and its population vulnerability in the United States.

Rising temperatures are associated with impaired sleep quantity and quality. Yet, little is known about population vulnerabilities. We aim to assess the sleep health associations with heat exposure and by sociodemographic, spatial, and health-related factors with projected future changes in the United States. This study linked longitudinal sleep records measured by digital wearables in the All of Us Research Program from 2010 to 2022 with gridded meteorological data. We assessed daily daytime and nighttime temperature anomalies as heat exposures. Sleep duration, continuity, onset, and stages associations with heat were assessed using multi-stage linear mixed effect models. Vulnerability to heat by sociodemographic, spatiotemporal, and health-related factors was estimated. We projected reductions in daily sleep duration from 2020 to 2099, under different future climate scenarios in U.S. by climate zones. This study included 14,232 adults with 12,531,244 nights of sleep duration and onset measurements and 8,134,295 sleep continuity and stage measurements in the continuous U.S. We found that a 10 °C increase of the daytime and nighttime temperature anomalies was associated with a decrease of 2.19 (95 % Confidence Interval (CI): 2.09, 2.29) and 2.63 (95 % CI: 2.51, 2.75) minutes of total sleep time, respectively. The effects of heat on sleep duration were greater (9.2 % - 79.4 %, p-value for interaction < 0.05) among females, Hispanics, and those with lower socioeconomic status or chronic health conditions. We also found substantial spatial differences, with the effect estimates being twice as large in marine climate zones compared with other regions. We project 8.5-24.0 additional hours of sleep reduction could occur per person-year in different climate zones by 2099 compared to the 1995-2014. Higher sleep duration reduction happened in June to September and in Marine climate zones on the west coast. This study highlighted adaptation inequalities across regions, sociodemographic and health-related factors.