Characterizing the spatial variability and vulnerability of heatwaves on ambulance callouts in Adelaide

Abstract

BACKGROUND AND AIM: High temperatures and heatwaves are associated with increased morbidity/mortality, and pose a substantial public health burden. Understanding the patterns of heatwave vulnerability at a fine spatial scale is essential to better target prevention strategies to areas with heightened vulnerability. This study aimed to investigate heatwave impacts on ambulance callouts in Adelaide at a small geographical level and identify area-level factors that influence the high morbidity risk within Adelaide. METHODS: Ambulance callouts data during the warm-season (October-March) from 2007 to 2014 were obtained from the South Australian Department for Health and Wellbeing. A time-stratified case-crossover design was used to examine associations between heatwave-severity (defined using Excess Heat Factor) and ambulance callouts at the Statistical Area Level 2 (SA2) spatial unit (representing suburbs). Effect modification by neighbourhood characteristics was examined and city-level estimates were pooled using random-effects meta-analyses. Results are reported as the percent increase in risk according to heatwave-severity (low-intensity, severe/extreme) compared with non-heatwaves, and were then mapped to produce a spatial representation of risk. RESULTS:A total of 377,125 ambulance callouts were included in the analysis. An exposure-response relationship was observed with ambulance callouts increasing by 5% (95%CI: 3-6%) and 8% (95%CI: 6-11%) during low-intensity and severe/extreme heatwaves, respectively. SA2s in western and southern Adelaide had higher risks during low-intensity heatwaves, while SA2s in southern and central Adelaide had higher risks during severe/extreme heatwaves. Analysis of area-level factors on heatwave and ambulance callouts revealed higher health impacts in areas (SA2s) characterized by high percentages of populations with high heat exposure, low socioeconomic status, poor housing and transport, vulnerable household composition, and poor health status. CONCLUSIONS:Our results show that ambulance callouts increased during heatwaves, but with a varying magnitude within Adelaide. The identified differential demographic, social, and environmental drivers of heatwave-morbidity calls for place-based prevention and adaptation strategies to reduce heatwave-related health burden. KEYWORDS: Heatwave, Morbidity,Spatial heterogeneity,Vulnerability, Case-crossover, Neighbourhood