Background: Access to green space (e.g., parks and gardens) has been associated with child health and wellbeing, whereas blue space (e.g., coasts, lakes, and rivers) is understudied. Our aim was to determine whether proximity to the coast was associated with primary school children's weight status, modifiable health-related behaviors, and health-related quality of life (HRQoL). Methods: Exploratory cross-sectional analysis of baseline data from the Whole of Systems Trial of Prevention Strategies for Childhood Obesity (WHOSTOPS) study, to estimate gender-specific differences in weight and behaviors across four bands of distance from the coast (<5 km, 5 to <25 km, 25 to <50 km, ≥50 km). Linear and logistic models, with robust standard errors, adjusted for school year level, area-level socioeconomic position and rurality, and allowing for distance by gender interaction were fitted on data from 1216 children (aged 8.5-13 years). Main outcomes were weight status (categorical), physical activity (PA) (categorical), and global HRQoL score (continuous). Results: Compared with girls living in towns ≥50 km from the coast, those living within 5 km had lower odds for overweight/obesity [odds ratio (OR) = 0.50; 95% confidence interval (CI): 0.37-0.67] and higher mean moderate-to-vigorous PA minutes (accelerometry) (β = 8.7; 95% CI: 2.0-15.5) and global HRQoL (β = 3.2; 95% CI: 1.4-5.0). Compared with boys living ≥50 km from the coast, those living within 5 km had higher odds of meeting self-reported PA guidelines (≥60 minutes/day) for ≥5 days (OR = 2.33; 95% CI: 1.75-3.10), and higher mean global HRQoL scores (β = 5.6; 95% CI: 1.9-9.3). Conclusions: Living close to the coast was associated with some favorable health outcomes and behaviors, which differed between girls and boys.

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