Is Excess Heat Factor A Good Indicator For Assessing Heatwave Related Health Outcomes In Western Australia?
Global climate change poses threats to human health. Heatwaves have killed more people in Australia than any other natural hazard. In Western Australia (WA), the Department of Health (DoH) has an emergency management obligation to monitor and manage the impact of heatwaves on populations at higher risk of suffering adverse effects from heat exposure. Currently there are no standardised indicators to assess the impact of heatwaves on health. An innovative indicator called Excess Heat Factor (EHF, an index providing a comparative measure of intensity, load, duration and spatial distribution of a heatwave event) is introduced to quantify excess heat exposure and its association with health outcomes in WA from 2006 to 2013.
A retrospective study design was used. Weather data were extracted from the Bureau of Meteorology. The emergency department (ED) data and the death data were sourced from the WA DoH data collection systems. Correlations and regression modellings were performed to investigate the associations between daily EHF, ED attendances and deaths.
During 2006-2013, there were 235 heatwave events (EHF>0) with the highest frequency (n=48) in 2011 and the most intense (EHF=11.5) in 2007. Poisson regression analysis showed that heatwave events were associated with a 4% increase in 3-day cumulative ED attendance rate (95%CI =1.025-1.058, P<0.0001) among 1,662,718 ED attendances and marginally associated with an excess 7-day cumulative death rate (95%CI= 0.981-1.447, P=0.078) among 32,836 deaths.
EHF is potentially a useful indicator to assess the effect of heatwaves at a population level on health outcomes, especially 3-day cumulative ED attendance rate. Further investigation into its effect on cause-specific rates and the influence of age, gender, socioeconomic status and occupation is needed to verify the usefulness of this indicator. The outcomes of this study will provide baseline information and methods to monitor improvements in WA heatwave management systems.