0277 Age-Related Changes in Light Exposure, Sleep and Circadian Timing: Findings from the EPISONO Cohort

Abstract Introduction Actimetry is a noninvasive technique that records the 24-hour rest-activity rhythm to estimate sleep and circadian parameters. Light exposure data can also be derived from these devices, providing an additional and valuable information for basic and clinical research. The aim of the present work was to describe light exposure, sleep and circadian timing across age groups in a sample representing São Paulo city population in terms of age, sex and socioeconomic status. Methods This study is a subset of the 769 individuals enrolled in the 4th edition of the São Paulo Epidemiologic Sleep Study (EPISONO) cohort, of which 404 participants were included (60% female; mean age: 49.42±14.90 years). Actimetry data was collected between 2018 and 2019. Sleep (onset and offset), circadian (predicted dim-light melatonin onset) and light exposure timing (onset of the 10 hours of greatest exposure-oM10) were extracted from the 7-day records (5 weekdays and 2 free days). Generalized linear models, controlled for sex, socioeconomic status, body mass index, season, and daylight-saving time, were applied to assess the effects of age groups (20-29, 30-39, 40-49, 50-59, 60-69 and 70-80 years). Results Significant differences in sleep timing were observed (p< 0.001). Participants in the 20-39 years category exhibited later sleep onset and offset compared to older ones. Young adults (20-29 years) had a significantly later light oM10 (p< 0.001) and circadian phase (p< 0.001) compared, respectively, to participants aged ≥40 years and all other age groups. Conclusion This population-based study identifies the age of 40 years as a potential turning point in circadian and light exposure patterns, marking a transition from delayed young-adult rhythms to advanced timing in middle and older adulthood. These findings highlight the importance of age-tailored interventions to support sleep and circadian health. Support (if any) Associação Fundo de Incentivo à Pesquisa (AFIP). Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).