Sex differences in the association of overweight/obesity with asthma and lung function in adolescents aged 10–18 years: a meta-analysis

Objective The global prevalence of overweight, obesity, and asthma in adolescents has increased rapidly. However, previous studies have reported inconsistent correlations between adiposity and respiratory indicators, and only a few meta-analyses have focused on sex-based disparities. In this study, we systematically assessed the associations of overweight and obesity with asthma and pulmonary function among adolescents aged 10–18 years and explored sex differences. Methods This study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) guidelines. Eligible observational studies were retrieved and screened. Odds ratios (ORs) were pooled for asthma, and standardized mean differences (SMDs; Hedges’ g ) were pooled for pulmonary function outcomes using random-effects models. Sex differences were evaluated with formal interaction tests. Subgroup, leave-one-out sensitivity, and Egger's regression analyses were performed, and evidence certainty was rated using Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Results Twelve studies were pooled for asthma: overweight and obesity were associated with higher odds of asthma incidence (OR = 1.26, 95% CI: 1.15–1.37), with significant regional ( P for interaction < 0.001) and sex ( P = 0.010) interactions; the association was stronger in females (OR = 2.11, 95% CI: 1.44–3.10) than in males (OR = 1.07, 95% CI: 0.75–1.52). For pulmonary function (six studies), the overweight/obesity group showed higher forced vital capacity (FVC; SMD = 0.35, 95% CI: 0.09–0.61) and forced expiratory volume in 1 s (FEV1; SMD = 0.23, 95% CI: 0.01–0.45) but lower FEV1/FVC (SMD = −0.27, 95% CI: −0.36 to −0.18), with no significant sex interaction for any outcome. No significant differences were observed for peak expiratory flow (PEF), forced expiratory flow at 75% of FVC (FEF75), or forced expiratory flow between 25% and 75% of FVC (FEF25–75). Small-study effects in the asthma pool were largely attributable to the regional subgroup structure. Four outcomes were rated moderate certainty and seven low certainty by GRADE. Conclusion Overweight and obesity are associated with higher odds of asthma incidence and an early obstructive pulmonary function pattern in adolescents. The asthma association is stronger in females, whereas no sex differences were detected for pulmonary function. Targeted screening of high-risk adolescent girls and further large-scale multicenter studies are warranted. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420261398331 , PROSPERO CRD420261398331.