The association between sibling characteristics and young females' physical activity

OBJECTIVES: This study examined the associations of sibling constellation variables (sex and relative age) with (i) the proportion of female children meeting physical activity guidelines and (ii) their context of weekend play (indoor quiet play and outdoor time). DESIGN: Observational study with cross-sectional design. METHODS: Data originated from the Mothers and their Children's Health (MatCH) study. This analysis focused on females aged 5-12 years who had 0-2 siblings (n = 1640). Generalised estimating equations were used to investigate associations between sibling constellation variables and physical activity outcomes, adjusted for child age and maternal education, income, and physical activity. RESULTS: Overall, 558 participants (34%) met physical activity guidelines. Compared to only children, participants with younger or mixed-aged siblings had higher odds of meeting physical activity guidelines (1.63, 95% confidence interval [CI]: 1.04-2.55 and 1.63, 95% CI: 0.99-2.67, respectively), whilst participants with older siblings engaged in less indoor quiet play (36 min/day, 95% CI: 16-56). There were no differences in time spent outdoors. Among participants with one sibling, those with a younger male sibling had 1.68 (95% CI: 1.03-2.73) times the odds of meeting physical activity guidelines than only children. CONCLUSIONS: These findings suggest sibling composition is associated with female children's physical activity levels. Given the persistent sex differences in physical activity levels, interventions focused on ensuring that female children have diverse opportunities for active play in the home environment that engage entire families and connect them with their peers could be key to reducing disparities.