Heterogeneity of child and adolescent asthma determinants across urbanization stages: a 21-year global analysis

Urbanization reshapes environmental exposures, lifestyle, and health systems, yet global evidence on how child and adolescent asthma risk factors evolve across development stages remains limited. Using panel data from 149 countries (2000–2020), this study applied clustering and coupling coordination analysis to identify stage-specific pathways of urbanization and air quality transitions. Generalized additive models were subsequently employed to explore the heterogeneity of asthma determinants across these stages. Four evolution stages were identified: Early Urbanization with Emerging Pollution (Cluster 1), Rapid Urbanization with Pollution Accumulation (Cluster 2), Decelerating Urbanization with Pollution Mitigation (Cluster 3), and Mature Urbanization with Pollution Control (Cluster 4). While PM₂.₅ peaked during the rapid stage, asthma incidence reached its maximum during the decelerating stage. Significant heterogeneity in risk factors emerged: Cluster 1 was driven by PM₂.₅ and a large youth population; Cluster 2 was dominated by the impact of PM₂.₅; Cluster 3 was characterized by high temperature and obesity as the primary risk factors; and Cluster 4 remained sensitive to temperature, with green space and wind speed identified as protective factors. These findings suggest that asthma incidence determinants exhibit distinct patterns across urbanization stages, transitioning from pollution-driven to climate and lifestyle-related vulnerabilities, necessitating stage-specific public health interventions.