Physical activity and childhood asthma control: Mediation and moderation role of body mass index

Background Physical activity (PA) may be associated with asthma management. Whether PA is associated with childhood asthma control is not well studied, and the role of body mass index (BMI) in this association remains unclarified. This study aimed to evaluate the association between PA and childhood asthma control and investigate the potential mediating and modifying role of BMI in the association. Methods This cross-sectional study involved 303 asthmatic children aged 5-14 years. Information on PA was collected from children. Asthma control was assessed using a valid questionnaire by children and their parents. Height and weight were objectively measured and BMI was calculated and classified. Multiple linear regression, mediation, and moderation analyses were performed. Results There was a positive association between PA and childhood asthma control with adjustment for variates (B = 0.144, p = .012). Mediation analysis indicated that BMI status negatively mediated the association (estimate = -0.656, 95% credit interval: -1.645, -0.006), and such indirect effect is lower than the direct effect (indirect effect/direct effect = 58.3%). No evidence of effect modification by BMI was observed (P-interaction = 0.516). Stratified analyses showed that the significant association was only observed in children with overweight/obesity (normal weight: B = 0.863, p = .189; overweight/obese: B = 1.494, p = .044). Conclusions Increased PA is associated with improved childhood asthma control, especially for children with higher BMI. BMI exhibited a negative effect but not effect modification in this association. PA should be encouraged to improve asthma control for asthmatic children. Besides, mechanisms other than weight loss may explain the association.