0772 Associations Between Solar Exposure and Sleep Architecture Among Black Adults

Abstract Introduction Black American adults experience marked sleep disparities situated within a context of unequal psychosocial and environmental burdens. Solar radiation, a major determinant of daytime thermal and light conditions, is an understudied environmental factor that may influence sleep architecture via circadian and thermoregulatory pathways. In this study, we examined the associations between daytime solar radiation and sleep architecture in a cohort of Black American adults. Methods We analyzed data from 363 Black American adults (266 females, 97 males; mean age 48.2±14.8 years) from two NIH-funded studies (ESSENTIAL and MOSAIC) conducted in South Florida and New York City. Participants wore SleepImage rings for one week; these devices provided data on sleep states from cardiorespiratory signals, and nightly data were averaged per participant. Percentages of time spent in stable/unstable NREM sleep, and REM sleep were used as sleep architecture outcomes. Daytime solar intensity was indexed by direct-beam sunlight at ground level (W/m²), estimated from the satellite-based NASA POWER project, linked to residential coordinates by date, and averaged over each participant’s monitoring period. Multivariable linear regression, adjusted for age, sex, employment status, marital status, income, and study site, estimated associations between direct sunlight exposure and the percentage of time spent in stable/unstable NREM sleep, and REM sleep. Results Greater direct sunlight was linked to more time spent in stable NREM sleep (β=15.2 percentage points per log-unit, p=0.004; adjusted R²=0.24) and less time spent in unstable NREM sleep (β=−10.9, p=0.012; adjusted R²=0.20) and REM sleep (β=−4.3, p=0.016; adjusted R²=0.18), with REM sleep time decreasing in parallel with unstable NREM sleep. These adjusted models indicate that daytime direct sunlight accounts for a meaningful fraction of between-person differences in sleep architecture. Conclusion Among Black American adults, greater daytime direct sunlight exposure was associated with more time spent in stable NREM sleep and less time in unstable NREM and REM sleep, consistent with a more consolidated sleep architecture profile. These patterns support a thermal pathway linking daytime environmental conditions to nocturnal sleep organization and highlight solar exposure as a relevant environmental factor in the context of sleep health disparities. Support (if any) NIH (R01HL142066 and R01AG067523).