The Impact Of Heat Waves On Mortality And The Effect Modification By Heat Waves Characteristics In Four Areas In Guangdong Province, China

Objective We analyze the impacts on mortality of heat wave in4areas (Nanxiong,Guangzhou, Zhuhai and Taishan) in Guangdong Province. We also aim to estimatewhether heat wave intensity, duration, or timing in season modifies the effect onmortality.Methods Daily meteorology data and mortality data were collected in2006-2010in4areas. The effect of heat waves included main effect due to independent effects ofhigh temperatures, and added effect due to sustained duration of heat during waves.Distributed lag non-linear model was fitted for each area to access the differentdelayed and cumulative effects of heat waves on mortality. The area-specific resultswere combined into one overall estimate using the meta-analytic techniques. Then wetested for differences by death causes, age groups and sex. We also estimate how heatwave intensity, duration, or timing in season modified the effect of heat wave onmortality.Results The overall estimated main effect was greater (RR=1.082,95%CI:1.034~1.132) than the added effect (RR=1.000,95%CI:0.962~1.04) on the currentdays. For main effect, heat waves effect was high in two county-level cities Nanxiongand Taishan but less in two areas Guangzhou and Zhuhai on the current day. For maineffect, an immediate relative risk decays during the first week, with the highestcumulative effect at lag2in Nanxiong, Zhuhai and Taishan and lag4in Guangzhou.Both the overall estimated heat wave effects in respiratory mortality andcardiovascular mortality were higher than total mortality. Estimated heat wave effectswere significantly higher in75years group and female population. On average,estimated heat wave mortality risk increased1.4%(95%CI:-0.6~3.4) for every1°Cincrease in heat wave intensity and1.2%(95%CI:-5.6~8.5) for a1day increase inheat wave duration. The estimated heat wave mortality risk decreased0.1%(95%CI: -1.2~1.0) for heat wave occurred every10days later in season.Conclusion Temperature explains most excess risk of mortality in the heat wavesperiods. Heat waves effect was high in Nanxiong and Taishan but less in Guangzhouand Zhuhai. Lag effects of heat waves were observed. Heat wave effects were higherin the respiratory and cardiovascular disorders,75years groups and femalepopulation. We observed no significant modifying effect of heat wave characteristics.