Abstract
This research analyzed the relationship between extreme heat and Emergency Medical Service (EMS) calls in King County, WA, USA between 2007 and 2012, including the effect of community-level characteristics. Extreme heat thresholds for the Basic Life Support (BLS) data and the Advanced Life Support (ALS) data were found using a piecewise generalized linear model with Akaike Information Criterion (AIC). The association between heat exposure and EMS call rates was investigated using a generalized estimating equations with Poisson mean model, while adjusting for community-level indicators of poverty, impervious surface, and elderly population (65+). In addition, we examined the effect modifications of these community-level factors. Extreme-heat thresholds of 31.1 °C and 33.5 °C humidex were determined for the BLS and ALS data, respectively. After adjusting for other variables in the model, increased BLS call volume was significantly associated with occurring on a heat day (relative rate (RR) = 1.080, p < 0.001), as well as in locations with higher percent poverty (RR = 1.066, p < 0.001). No significant effect modification was identified for the BLS data on a heat day. Controlling for other variables, higher ALS call volume was found to be significantly associated with a heat day (RR = 1.067, p < 0.001), as well as in locations with higher percent impervious surface (RR = 1.015, p = 0.039), higher percent of the population 65 years or older (RR = 1.057, p = 0.005), and higher percent poverty (RR = 1.041, p = 0.016). Furthermore, percent poverty and impervious surface were found to significantly modify the relative rate of ALS call volumes between a heat day and non-heat day. We conclude that EMS call volume increases significantly on a heat day compared to non-heat day for both call types. While this study shows that there is some effect modification between the community-level variables and call volume on a heat day, further research is necessary. Our findings also suggest that with adequate power, spatially refined analyses may not be necessary to accurately estimate the extreme-heat effect on health.
Highlights
According to the United States Climate and Health Assessment [1], the US annual average temperatures are predicted to rise at least 1.7 ◦ C by the end of the century with chances of a5.6 ◦ C increase depending on many factors such as future emissions of greenhouse gases
The results essentially suggested that the relative rate of daily Advanced Life Support (ALS) call volumes between a heat day and a non-heat day differ across various level of impervious surfaces or percent poverty
After refining our exposure assessment, and adjusting for community-level characteristics, our analysis observed the same 1.08 Relativerate rate (RR) for Basic Life Support (BLS) calls, but a much lower 1.067 RR for ALS calls on heat days compared to non-heat days
Summary
According to the United States Climate and Health Assessment [1], the US annual average temperatures are predicted to rise at least 1.7 ◦ C by the end of the century with chances of a. 5.6 ◦ C increase depending on many factors such as future emissions of greenhouse gases. With this temperature increase, will come more frequent and intense heat waves along with harmful effects to human health. Scientists predict for every doubling of carbon dioxide, it is likely that there will be a 1.9 to 4.5 ◦ C increase in temperature [2,3]. Sherwood and Huber [4], argued a global mean. Res. Public Health 2017, 14, 937; doi:10.3390/ijerph14080937 www.mdpi.com/journal/ijerph
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