Evaluating the association between heatwave vulnerability index and related deaths in Australia

Abstract

Heatwaves affect public health. Previous human heat vulnerability assessment studies, mostly focused in urban areas, suggest association with heat-related deaths. However, these associations have not been thoroughly examined in Australia. We examined the association between heatwave vulnerability index (HVI) and risk of heatwave-related deaths across Australia.

Seasonal (December–February) all-cause mortality and heatwave data across 2189 Statistical Area Level 2 (SA2s) spatial units were acquired from 2001 to 2019. We also used SA2 level heatwave vulnerability index (HVI) data estimated from 2021 national census data and heatwave data (2001–2019) across Australia. In each SA2, we calculated seasonal mortality rates using the empirical Bayes smoothing approach to account for spatial variations in deaths. We then used a quasi-Poisson regression model to quantify the mortality rates associated with SA2-specific heatwave days across Australia. Finally, we used a linear regression analysis to examine the association between HVI and heatwave-related deaths. We observed an association between HVI (β: 0.18, 95 % CI: 0.08–0.27) and increased in percentage (%) of heatwave-related deaths across the capital cities. A unit increase in HVI -associated deaths was higher under severe heatwave days (β: 0.39, 95 % CI: 0.05–0.74) compared to low-intensity heatwave days (β: 0.21, 95 % CI: 0.09–0.32). We also found that the HVI component factor formed by low education, low income, low healthcare professionals, and diabetes prevalence is strongly associated with all the heatwave-related deaths in the capital cities. In an Australia-wide analysis, we did not find an association (β: -0.06, CI: −0.17-0.05) between HVI and risk of heatwave-related death. However, there was evidence of stronger association between HVI component factor formed by Indigenous population exposed to longer heatwave days and increased % of heatwave-associated deaths. HVI is positively associated with heatwave-related deaths in Australia, particularly in capital cities. Heatwave management strategies should include HVI maps to help protect communities against heatwave-related death, and morbidity.