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The Unfolding Story of Heatwaves in Adelaide: Severity, Duration, and Useful Triggers for Community Intervention

Nitschke, Monika1; Tucker, Graeme1; Hansen, Alana2; Williams, Susan2; Bi, Peng2

doi: 10.1097/01.ede.0000391698.57812.dd
Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Climate Change and Environmental Health

1Department of Health, South Australia, Australia; and 2University of Adelaide, South Australia, Australia.

Abstracts published in Epidemiology have been reviewed by the societies at whose meetings the abstracts have been accepted for presentation. These abstracts have not undergone review by the Editorial Board of Epidemiology.


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Two extreme heatwaves occurred in South Australia in 2008 and 2009. It is of interest how these 2 unprecedented heatwaves compare to averaged heatwave risks preceding these events. Dose-response effects of duration (increasing number of days within a heatwave) and intensity (by increments of 1°C above 35°C) of heatwaves (1993–2008) were also examined. Weather-based heatwave triggers were explored to inform relevance of current intervention measures.

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Using case-series analysis, daily morbidity and mortality rates during heatwaves were compared with rates during non-heatwave periods within the respective years and restricted to the warm season (October–March). Health outcomes examined were total, age group and disease-specific hospital admissions, emergency presentations, ambulance call-outs, and mortality. Heatwave definition was maximum temperature ≥35°C for 3 or more days.

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Ambulance call-outs during the 2 extreme heat events significantly exceeded call-outs from averaged preceding heatwaves affecting mainly cardiac and neurologically related call-outs. Only small increases in total hospital and emergency visits were observed. Renal admissions were increased substantially in both clinical settings, particularly in the older age groups. Direct heat-related admissions increased 14-fold for hospital admissions and 12-fold for emergency presentations in 2009 compared to 3-fold during averaged heatwaves. Increases in total mortality were restricted to the 2009 heatwave (10%; 95% CI: 0.99–1.22; P = 0.09). The major impact occurred in the 15–64 yrs age group, where mortality increased by 37% (95% CI: 1.09–1.71; P = 0.01). Older age groups were not affected. Significant dose-response relationships were observed for duration (ambulance, hospital and emergency setting) and for intensity (ambulance and mortality). Mortality started to increase at average temperature 31°C (average of daily maximum and minimum; 3 or more days).

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These findings indicate a higher level of health risk during the recent severe heatwaves in Adelaide than in previous heatwaves. Evaluation of health outcomes in relation to relevant thresholds will guide future community interventions.

© 2011 Lippincott Williams & Wilkins, Inc.