Sleep Duration and Sun Exposure in Portuguese Children: Associations With Obesity Indicators.

INTRODUCTION: Sleep duration, sun exposure, and obesity are important and potentially interconnected factors in child health. In this study, we aimed to analyze the associations between sleep duration, sun exposure, and obesity indicators in Portuguese children. METHODS: This cross-sectional study included 4755 children aged 3-10 years from public and private schools across Portugal. Parents reported children's sleep duration, sun exposure, screen time, active play, and physical activity using validated questionnaires. Trained professionals measured weight and height to calculate Body Mass Index (BMI) and assessed skinfold thickness to estimate body fat percentage (%BF). Multiple linear regression analyses, stratified by sex and adjusted for demographic, behavioral, and anthropometric factors, analyzed associations between sun exposure and sleep duration. RESULTS: In partially adjusted models (Model 1), negative associations persisted among boys, and positive associations emerged in girls for average sleep duration (β = 2.11; 95% CI: 0.25 to 3.96; p = 0.026) and weekdays (β = 2.40; 95% CI: 0.47 to 4.33; p = 0.015). In fully adjusted models (Model 2), the negative association remained only for boys on Sundays (β = -4.57; 95% CI: -8.22 to -0.91; p = 0.014), with no significant associations in girls. CONCLUSIONS: Sun exposure exhibits modest, sex-specific associations with sleep duration in children. These findings emphasize the importance of considering behavioral and environmental factors when designing interventions to promote healthy sleep, support growth, and prevent childhood obesity.