Heatwave-related mortality among older Australians: A Two-Stage Small-Area Time Series Analysis
1
School of Public Health, Adelaide University, Adelaide, Australia
Popul. Med. 2026;8(Supplement Supplement 1):
ABSTRACT
INTRODUCTION:
Older adults are particularly vulnerable to heat exposure, yet evidence on the magnitude and spatial heterogeneity of heat-related mortality across Australia remains limited. ¹, ² Excess Heat Factor (EHF), the national heatwave metric, captures both short-term and acclimatisation-adjusted heat stress ³ but has not been applied in fine-scale mortality analyses among older populations. This study aimed to quantify heatwave-related mortality among Australians aged ≥65 years from 1 January 2012 to 31 December 2022, accounting for regional variation.
METHODS:
A two-stage case time series analysis was conducted. In the first stage, quasi-Poisson conditional time-series models were fitted for Australian Statistical Area Level 3 (SA3) regions, with EHF modelled using distributed lag non-linear models over lags 0–7 days. In the second stage, area-specific estimates were pooled using multivariate meta-regression with principal component analysis to account for spatial heterogeneity and to derive national exposure–response relationships, which were used to inform small-area spatial mapping.
RESULTS:
Between 2012 and 2022, a total of 1 450 271 deaths occurred among adults aged ≥65 years, predominantly in major cities and temperate climate zones. Across states and territories, both heatwave intensity and the number of heatwave days varied substantially. Preliminary pooled results showed a non-linear association between heatwave intensity and mortality risk, with increasing risk at higher EHF values. Over lags 0–7 days, relative risks compared with the non-heatwave reference (EHF = 0) were 1.09 (95% CI: 1.03–1.14) at the severe heatwave threshold (EHF = 15 K²) and 1.31 (95% CI: 1.14–1.50) at the extreme threshold (EHF = 31 K²).
CONCLUSIONS:
This study provides a nationwide small-area assessment of heat-related mortality risk among older Australians, showing substantially higher mortality during severe and extreme heatwave conditions. These findings can inform targeted heatwave preparedness and adaptation strategies for ageing populations.
Older adults are particularly vulnerable to heat exposure, yet evidence on the magnitude and spatial heterogeneity of heat-related mortality across Australia remains limited. ¹, ² Excess Heat Factor (EHF), the national heatwave metric, captures both short-term and acclimatisation-adjusted heat stress ³ but has not been applied in fine-scale mortality analyses among older populations. This study aimed to quantify heatwave-related mortality among Australians aged ≥65 years from 1 January 2012 to 31 December 2022, accounting for regional variation.
METHODS:
A two-stage case time series analysis was conducted. In the first stage, quasi-Poisson conditional time-series models were fitted for Australian Statistical Area Level 3 (SA3) regions, with EHF modelled using distributed lag non-linear models over lags 0–7 days. In the second stage, area-specific estimates were pooled using multivariate meta-regression with principal component analysis to account for spatial heterogeneity and to derive national exposure–response relationships, which were used to inform small-area spatial mapping.
RESULTS:
Between 2012 and 2022, a total of 1 450 271 deaths occurred among adults aged ≥65 years, predominantly in major cities and temperate climate zones. Across states and territories, both heatwave intensity and the number of heatwave days varied substantially. Preliminary pooled results showed a non-linear association between heatwave intensity and mortality risk, with increasing risk at higher EHF values. Over lags 0–7 days, relative risks compared with the non-heatwave reference (EHF = 0) were 1.09 (95% CI: 1.03–1.14) at the severe heatwave threshold (EHF = 15 K²) and 1.31 (95% CI: 1.14–1.50) at the extreme threshold (EHF = 31 K²).
CONCLUSIONS:
This study provides a nationwide small-area assessment of heat-related mortality risk among older Australians, showing substantially higher mortality during severe and extreme heatwave conditions. These findings can inform targeted heatwave preparedness and adaptation strategies for ageing populations.
| eISSN: | 2654-1459 |
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