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

In partially adjusted models, positive associations between sun exposure and average sleep duration emerged in girls.

• β = 2.11; 95% CI: 0.25 to 3.96; p = 0.026 for average sleep duration in girls
• β = 2.40; 95% CI: 0.47 to 4.33; p = 0.015 for weekday sleep duration in girls
• These associations did not persist in the fully adjusted models (Model 2)
• Analyses were stratified by sex and adjusted for demographic, behavioral, and anthropometric factors

In partially adjusted models, negative associations between sun exposure and sleep duration persisted among boys.

• Negative associations among boys were present in Model 1 (partially adjusted)
• The direction of association differed by sex, with boys showing negative and girls showing positive associations
• Sex-stratified multiple linear regression analyses were used to identify these patterns

In fully adjusted models, a significant negative association between sun exposure and sleep duration remained only for boys on Sundays.

• β = -4.57; 95% CI: -8.22 to -0.91; p = 0.014 for Sunday sleep duration in boys
• No significant associations were found in girls in the fully adjusted model
• Model 2 was adjusted for demographic, behavioral, and anthropometric factors including screen time, active play, and physical activity

The study included 4755 Portuguese children aged 3–10 years from public and private schools across Portugal.

• Cross-sectional study design
• 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 BMI
• Skinfold thickness was assessed to estimate body fat percentage (%BF)

Obesity indicators assessed included both BMI and body fat percentage estimated from skinfold thickness.

• BMI was calculated from professionally measured weight and height
• Body fat percentage (%BF) was estimated using skinfold thickness measurements
• Multiple linear regression analyses examined associations between sun exposure and sleep duration as they relate to these obesity indicators
• Analyses were stratified by sex

Sun exposure associations with sleep duration were found to be modest and sex-specific in children.

• The authors characterized the associations as 'modest, sex-specific associations with sleep duration in children'
• Significant associations differed not only by sex but also by day of the week (weekdays vs. Sundays)
• The findings emphasize 'the importance of considering behavioral and environmental factors when designing interventions to promote healthy sleep, support growth, and prevent childhood obesity'