Heatwaves and emergency department utilisation in Queensland: a 10-year retrospective study

Globally, temperatures are increasing due to the effects of climate change. Extreme heat is a public health threat, increasing the burden on health systems during heatwaves, and the days following. Australia is susceptible to extreme heat and must plan accordingly to ensure health systems can respond as heatwave conditions increase in frequency, severity, and duration. This study investigates the impact of heatwaves on Emergency Department (ED) presentations in the state of Queensland, Australia, considering key demographic, clinical, and temporal factors.

Warm-season (November-March) ED presentations (2010-19) obtained from Queensland Health at the postcode level were analysed in relation to heatwaves. Heatwaves were defined using the Excess Heat Factor, a metric designed by the Australian Bureau of Meteorology. Quasi-Poisson regression models produced incidence rate ratios (IRRs) with 95% confidence intervals (CIs) to quantify differences in ED demand between heatwave and non-heatwave days. Subgroup analyses were conducted by heatwave severity, rurality, sex, age, primary diagnosis, triage category and financial year.

There was a 10.47% (IRR_adj: 1.10; 95% CI: 1.10, 1.11) increase in ED presentations on heatwave days. The effect was greatest during extreme heatwaves (IRR_adj: 1.23; 95% CI: 1.20, 1.26). There was a direct relationship between increasing impact and rurality, with those living in very remote areas most impacted, experiencing a 54.26% increase in ED presentations in comparison to non-heatwave days (IRR_adj: 1.54; 95% CI: 1.50, 1.59). There was no clear age-related trend, and no significant variation by sex. Presentations increased on heatwave days for most primary diagnoses, with the most notable increase observed in cases classified under 'endocrine, nutritional, and metabolic disorders' (IRR_adj: 1.27; 95% CI: 1.24, 1.29). The least urgent triage category (category 5) exhibited the most significant increase in ED incidence on heatwave days (IRR_adj: 1.27; 95% CI: 1.25, 1.29). Temporal trends showed that the 2015-16 financial year (IRR: 1.13; 95% CI: 1.12, 1.15) demonstrated the greatest increase in ED incidence on heatwave days.

Emergency departments must prepare for higher numbers of people presenting during heatwaves. The variability in impact across different demographic, clinical, and temporal factors underscores the complex relationship between heatwaves and health system demand. As climate change intensifies heatwaves, future research, including prospective studies, will be needed to provide essential evidence to inform public health planning.