Municipal heat stress and respiratory mortality in Central Brazil assessed by an integrated environmental vulnerability index

<title>Abstract</title> <p>Heat exposure is intensifying under climate change and poses increasing risks to urban populations. We assessed municipal heat stress across the 79 municipalities of Mato Grosso do Sul, Central Brazil, using a composite Urban Heat Stress Index (UHSI) that integrates climatic exposure and environmental buffering capacity. Ecological data from 2023 were analysed using heteroskedasticity-robust linear regression adjusted for Human Development Index (HDI), income inequality, and population size. Municipal heat stress showed marked spatial variation, with the highest values concentrated in the western and northwestern regions of the state. Higher heat-stress levels were associated with increased respiratory mortality (β = 10.7 deaths per 100,000 inhabitants per one-standard-deviation increase; 95% CI: 1.48–19.92; p = 0.024). No association was observed for cancer mortality (p = 0.923), supporting the specificity of the findings. Municipalities classified in the highest heat-stress group also exhibited the greatest respiratory mortality burden. These findings suggest that integrating climatic exposure with environmental buffering improves the identification of climate-related respiratory vulnerability beyond temperature-based indicators alone. Because it is based on readily available environmental information, the UHSI provides a practical framework for supporting municipal public health planning, climate adaptation, urban greening, and heat-health preparedness.</p>