Defining region-specific heatwave in China based on a novel concept of “avoidable mortality for each temperature unit decrease”

Abstract

The distribution of temperature and temperature-health association varied largely across different regions in China, a region-specific definition for heatwave was therefore needed. We collected the data on daily mortality, meteorological factors and air pollution in 84 Chinese cities during 2013–2016, which was divided into seven regions. Based on the association between daily maximum temperature and mortality in each city in a threshold distributed lag non-linear model, where the threshold was defined as the temperature corresponding to the lowest mortality risk, we calculated the number of deaths that could be avoided for 1 °C decrease in maximum temperature under different thresholds, then a random-effect meta-analysis was used to generate regional results, in which the temperature with the highest avoidable mortality number for 1 °C decrease was considered as the most appropriate heatwave definition. We observed an immediate detrimental effect of high temperature within three lag days. Our analysis suggested to use 29.5 °C, 31.5 °C, 29.0 °C, 31.5 °C, 30.0 °C, and 28.5 °C as the heatwave standard for east, north, northeast, central, south, and southwest region, with the avoidable mortality number of 1.54 (95 % Confidence interval (CI): 0.88, 2.19), 0.55 (95 % CI: 0.16, 0.94), 0.59 (95 % CI: 0.32, 0.86), 1.14 (95 % CI: 0.68, 1.59), 1.22 (95 % CI: 0.54, 1.90), and 0.78 (95 % CI: 0.01, 1.55), respectively, while the estimated number 0.19 (95 % CI: −0.02, 0.40) in northwest region was not statistically significant. The concept of ‘avoidable mortality for 1 °C decrease’ was proposed to define the heatwave event, and varied maximum temperature between 28.5 and 31.5 °C was suggested for region-specific heatwave definition in China.

Keywords

• Heatwave
• Mortality burden
• Distributed lag non-linear model