The Impact of Heat and Bushfire Smoke on Health System Utilisation in Australia

To characterise the associations of heat and bushfire smoke with health services utilisation and medication use at a national scale to support Australia's first National Climate Risk Assessment.

Cross-sectional, population study, covering health conditions with the highest burden of disease.

People in Australia accessing public health services between 2014 and 2020 for care related to cardiovascular, respiratory and mental health conditions.

Relative risks of heat and bushfire smoke (particulate matter ≤ 2.5 μm in diameter [PM_2.5]) on health system utilisation and medication use, measured as emergency department (ED) presentations, hospital inpatient admissions, Medicare Benefits Schedule service claims in primary care and Pharmaceutical Benefits Scheme prescriptions dispensed. Relative risks (RRs) and 95% confidence intervals were estimated for short-term lags between exposure periods and health system usage.

Heat was most strongly associated with ED presentations, with a RR of 1.033 (95% CI, 1.023-1.043; p < 0.001) per degree temperature change for respiratory conditions and 1.023 (95% CI, 1.016-1.031; p < 0.001) for mental health conditions. PM_2.5 at a 1-day lag had the highest association with hospital admissions, with a RR of 1.014 per 1 μg/m³ change in particulate density for both cardiovascular (p = 0.001) and respiratory (p = 0.002) conditions. Primary care visits for mental health conditions were strongly associated with levels of PM_2.5 (RR, 1.049 [95% CI, 1.040-1.058]; p < 0.001) and with temperature (RR, 1.027 [95% CI, 1.014-1.039]; p < 0.001), while medication use increased across respiratory, cardiovascular and mental health categories in response to both exposures, with particulate matter showing stronger effects for cardiovascular, respiratory and mental health prescriptions. Mental health outcomes consistently showed vulnerability across all domains.

Heat was strongly associated with acute ED presentations, while particulate matter was strongly associated with hospital admissions and medication use. Mental health services are broadly sensitive to both exposures. These findings emphasise the need for integrated air quality management and heat-health polices to reduce system-wide health burdens.