Local climate modifies associations between environmental exposures and paediatric asthma hospitalisation

Paediatric asthma hospitalisations have marked seasonal peaks, but it remains unclear whether associations with environmental exposures vary under different local climatic conditions. This study aimed to quantify regional- and season-specific associations between environmental factors and paediatric asthma hospitalisations. We conducted a retrospective ecological time-series study in Australia using statewide inpatient administrative records, including all asthma hospitalisations among children and adolescents from 2003 to 2019 in three previously identified high-risk local government areas with contrasting climatic characteristics. Environmental exposures included meteorological variables, air pollutants, and vegetation greenness. Associations were estimated using distributed lag non-linear models, and random forest was used to assess predictor importance. A total of 11,177 hospitalisations were analysed. Environmental associations showed substantial regional and seasonal heterogeneity. Higher vegetation greenness was associated with increased hospitalisation risk across all regions, with the strongest association observed in the tropical monsoon/rainforest region (IRR 1.65, 95% CI 1.29–2.11). Higher mean temperature was inversely associated with risk in all regions, with an estimated 5–8% lower risk per 1 °C increase. By contrast, air pollutant effects were region- and season-dependent, with the largest estimates observed in the tropical savannah wet season, particularly for SO₂ (IRR 2.11, 95% CI 1.56–2.85). Variable-importance analyses consistently identified vegetation greenness and temperature as leading predictors across climatic settings. These findings suggest that associations between environmental exposures and paediatric asthma hospitalisations vary by region and season. Local climatic context may partly explain this heterogeneity, supporting further investigation of region- and season-specific approaches to asthma risk surveillance and prevention.