Mapping heatwave-related mortality across 2288 local communities in Australia: a nationwide time-series analysis

Heatwaves are becoming more frequent and intense in a warming climate and can cause substantial excess deaths. This study aimed to assess and map heatwave-related mortality burdens across Australia.

Heatwaves were defined as periods of ≥2 consecutive days with daily mean temperatures above the 95th percentile for each community (SA2 or SA3 level) during 2009-2019. A two-stage time-series design was used to estimate heatwave-mortality associations during warm seasons (November to March). In first-stage, a Poisson regression model estimated lagged (0-10 days) heatwave effects on daily mortality for each SA3. In second-stage, SA3-specific estimates were pooled using a random-effects meta-analysis to derive national estimates and generate best linear unbiased predictions (BLUPs) for each SA3. These SA3-level estimates were then assigned to corresponding SA2s. Due to boundary changes in 2016, mortality burden was estimated only for 2016-2019.

We analysed 249,546 death records (47.9% female, median age 81) from 2,288 SA2 communities between 2016 and 2019. The pooled relative risk of heatwaves on all-cause mortality over lag 0-10 was 1.05 (95% CI: 1.02-1.08). An estimated 1,009 deaths (95% empirical CI: 903-1,052) were attributable to heatwaves, equivalent to a national attributable mortality rate of 1.08 (95% CI: 0.97-1.13) deaths per 100,000 residents per year. Queensland and New South Wales had the highest attributable mortality rates-over three times those in Western Australia. Communities with higher proportions of elderly residents, gender imbalance, individuals needing assistance, and lower income or education experienced higher mortality burdens.

Heatwave-related mortality burdens varied substantially across Australian communities. These findings provide essential evidence for targeted public health interventions to address rising heatwave-related health risks under climate change.