Abstract
Extreme heat is intensifying under climate change, yet evidence on regional and temporal variation in heat-related morbidity remains limited. Here we analyzed over 100 million emergency department (ED) visits across five countries and territories from 2000 to 2019 using a time-stratified case-crossover design to quantify associations between summer temperature and acute healthcare demand. Here we show that higher summer temperatures are associated with increased risks of ED visits across all study regions. At the 95th percentile of local daily maximum temperature, cumulative excess odds ratios are highest in Australia (42.1%, 95% confidence interval 38.1-46.2) and Taiwan (25.7%, 16.7-35.3), followed by Brazil (18.0%, 17.6-18.4), New Zealand (16.6%, 13.5-19.7), and Canada (6.1%, 4.1–8.1). Over time, heat-related risks declined in Australia but increased in Brazil. These findings reveal substantial regional and temporal heterogeneity in vulnerability and underscore the need for locally tailored heat-health adaptation strategies under a warming climate.
Funding
Y.G. discloses support for publication of this work from the Australian Research Council (DP210102076) and the National Health and Medical Research Council (APP2000581, GNT2008813). W.H., Y.W., and B.W. disclose support for publication of this work from the China Scholarship Council (202006380055 for W.H.; 202006010044 for Y.W.; 202006010043 for B.W.). R.X. discloses support for publication of this work from the VicHealth Postdoctoral Research Fellowship (2022). Z.Y. and Z.X. disclose support for publication of this work from the Monash Graduate Scholarship and the Monash International Tuition Scholarship. Y.Z. discloses support for publication of this work from the National Health and Medical Research Council e-Asia Joint Research Program (GNT2000581). W.Y., P.Y., T.Y., and S.Z. disclose support for publication of this work from the Monash Faculty of Medicine, Nursing and Health Sciences Early Career Postdoctoral Fellowships. S.L. discloses support for publication of this work from the National Health and Medical Research Council Emerging Leader Fellowship (GNT2009866).
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Yu, W., Xu, R., Huang, W. et al. Regional variations in emergency care vulnerability to summer heat. Nat Commun (2026). https://doi.org/10.1038/s41467-026-73338-z
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DOI: https://doi.org/10.1038/s41467-026-73338-z
