Impact of heatwave intensity using excess heat factor on emergency department presentations and related healthcare costs in Adelaide, South Australia

Background: The health impacts of heatwaves are a growing public health concern with the frequency, intensity, and duration of heatwaves increasing with global climate change. However, little is known about the healthcare costs and the attributable morbidity associated with heatwaves Objective This study aims to examine the relationship between heatwaves and costs of emergency department (ED) presentations, and to quantify heat-attributable burden during the warm seasons of 2014–2017, in Adelaide, South Australia. Methods: Daily data on ED presentations and associated costs for the period 2014–2017 were obtained from the South Australian Department of Health and Wellbeing. Heatwave intensity was determined using the excess heat factor (EHF) index, obtained from the Australian Bureau of Meteorology. A distributed lag non-linear model (DLNM) was used to quantify the cumulative risk of heatwave-intensity over a lag of 0–7 days on ED presentations and costs. Effects of heatwaves were estimated relative to no heatwave. The number of ED presentations and costs attributable to heatwaves was calculated separately for two EHF severity categories (low-intensity and severe/extreme heatwaves). Subgroup analyses by disease-diagnosis groups and age categories were performed. Results: For most disease diagnosis and age categories, low-intensity and severe heatwaves were associated with higher rates of ED presentations and costs. We estimated a total of 1161 (95% empirical confidence interval (eCI): 342, 1944) heatwave-attributable all-cause ED presentations and associated healthcare costs (thousands) of AU$1020.3 (95% eCI: 224.9, 1804.7) during the warm seasons of 2014–2017. The heat-related illness was the disease category contributing most to ED presentations and costs. Age groups 0–14 and ≥ 65 years were most susceptible to heat. Conclusions: Heatwaves produced a statistically significant case-load and cost burden to the ED. Developing tailored interventions for the most vulnerable populations may help reduce the health impacts of heatwaves and to minimise the cost burden to the healthcare system.