Heatwave-related morbidity in Australia: Effect modification by Individual and Area-level factors

Abstract

Abstract Background Heatwaves are associated with increases in mortality, emergency department visits, and hospital admissions. However, evidence regarding heatwave impacts on general practice (GP) visits is limited. The objectives of this study were to quantify the impact of heatwaves on GP visits in Australia and identify the individual and area-level factors that modify the heatwave-GP visits association. Methods Warm-season (October-March) GP visits data (2011-2016) were obtained from the Australian Bureau of Statistics. Using a case-crossover approach we assessed the effect of heatwaves (defined using Excess Heat Factor) on GP visits at the Statistical Area Level 2 (SA2) spatial unit (reflecting suburbs), as well as effect modification by individual and area-level factors. Results are reported as percent increase in GP visits during severe/extreme heatwaves compared with non-heatwaves. Results Nationally, GP visits increased by 4% (95%CI: 3-4%) during severe/extreme heatwaves. But impacts varied with the highest effect observed in Canberra (16.4%; 95%CI:15.4-17.4%), Adelaide (14.9%; 95%CI: 14.3-15.4%), and regional Victoria (13.5%; 95%CI: 13-14%). A gradient of impact was found within locations, for example, vulnerable SA2s nationally were featured by a higher proportion of populations with no air-conditioning, low income, limited English proficiency, living alone, and a prevalence of diabetes and circulatory diseases. Individual-level factors included those: living alone, with limited English proficiency, with diabetes, hypertension and using anti-coagulants and diuretic medications. Conclusions Heatwaves increase GP visits in Australia, with impacts varied between locations and populations, affecting certain areas and individuals disproportionately. Our results using an individual and area-level linked data suggest that local area and individual vulnerabilities should be incorporated when developing place-based interventions combating heatwave-health impacts. Key messages Heatwaves increase GP visits in Australia, but with spatial variability across and within locations. Individual and area-level factors contribute to heatwave-vulnerability.