Effects of extreme temperature and humidity on COPD mortality: A multi-county study in Chongqing, China

Objective: This study assessed the associations between extreme temperature, humidity, and Chronic obstructive pulmonary disease (COPD) mortality and their spatial variation, within the understudied context of a mountainous city with complex microclimates. Methods: We conducted an ecological study across 38 counties in Chongqing (2015-2020), using a two-stage approach combining distributed lag nonlinear models and multivariate meta-regression to estimate county-specific and pooled associations. Results: Both extreme temperature and humidity were linked to increased COPD mortality. The cumulative relative risks (CRRs) for extreme high and low temperatures were 1.52 (95% CI: 1.27,1.83) and 1.39 (95% CI: 1.19,1.62), respectively. High and low humidity effects were weaker, with CRRs of 1.13 (95% CI: 0.97,1.31) and 1.12(95% CI: 0.85,1.48). Spatial heterogeneity was evident: heat effects occurred in urban and southeastern mountainous areas, cold risk was pronounced at higher altitudes, high humidity effects appeared along rivers, and low humidity increased risk in dry mountainous zones. Conclusions: Extreme temperature and humidity significantly influence COPD mortality, with clear spatial variability across regions. Our findings can support public health agencies and local governments in developing more targeted warning systems and improving climate-adaptive COPD prevention strategies.