Heat and Health Service Use: A Spatiotemporal Analysis

Background: While acute heatwaves are known to affect hospital presentations, less is known about broader health service use, regional disparities, or the effects of chronic climatic heat. Methods: We analysed 20 years of weekly health service use data between 2002 and 2022 across all Australian Statistical Areas Level 4 (SA4s) geographies for four major health services: medical services (MBS), pharmaceuticals (PBS), hospital admissions, and emergency department (ED) presentations - by clinical category (cardiovascular, respiratory, mental health, other). Three population-weighted weather metrics were measured: weekly maximum temperature, heatwave events, and long-term climatic averages. Fixed-effects panel models were used to estimate short-term impacts of weather metrics on health service use while cross-sectional models were used to assess chronic exposure effects. Findings: Acute exposure to dry temperature heatwaves was consistently associated with increased ED and inpatient presentations for mental health, cardiovascular, and other conditions. Apparent temperature heatwaves, incorporating humidity, showed more variable effects. MBS consultations rose modestly, while PBS dispensing declined during heat events. Long-term exposure to higher average temperatures was linked to increased inpatient care even after adjusting for socioeconomic status, remoteness, and health workforce. Disadvantaged regions experienced amplified effects, while areas with higher outdoor work exposure showed suppressed mental health care use. Interpretation: Both acute and chronic heat exposures influenced health service demand across services and geographies during the study period. Heatwaves exacerbate existing healthcare inequalities and can disrupt access to medicines. Adaptation strategies must extend beyond hospitals to include primary and community-based care, with attention to population vulnerability and regional climate. Funding: The International Centre for Future Health Systems receives funding from The Ian Potter Foundation.