Association of Sunlight Exposure with Sleep Hours in Iranian Children and Adolescents: The CASPIAN-V Study.

We aimed to assess the association of sunlight exposure with sleep duration and sleep onset time in children. Data were obtained from the fifth survey of a national school-based surveillance program in Iran. Sunlight exposure time, sleep duration, sleep onset time, physical activity time, mental health status and frequency of consuming coffee and tea were recorded. Overall, 14 274 students aged 7-18 years were recruited. Sleep duration was associated positively with sex, age, body mass index and physical activity, as well as with sunlight exposure and negatively with the consumption of coffee and tea. Higher physical activity, exposure to sunlight and mental status score in children exposed to sunlight via their face, hands, arms and feet, reduced the likelihood of sleep onset time after midnight (odds ratio (OR) = 0.909, 0.741 and 0.554 respectively). Daily exposure to sunlight may increase sleep duration and advance the sleep onset time in children and adolescents.