The assessment of current mortality burden and future mortality risk attributable to compound hot extremes in China

Global warming may increase the frequency of compound hot extremes (CHEs). This study aimed to assess the current mortality burden and future mortality risk attributable to CHEs in China. Daily meteorological, air pollution and mortality data were collected in 364 locations from 2006 to 2017 across China. Hot day/night was identified as a day where daily Tmax/Tmin was higher than its 90th percentile in summer. CHE was defined as a hot night with a following hot day. Mortality risk attributed to CHEs in each location was first evaluated using a distributed lag non-linear model. Location-specific association was pooled using a multivariate meta-analysis model, and attributable fraction in the current time and mortality risk from CHEs under different climate change scenarios (RCP 2.6, RCP 4.5, RCP 8.5) in the future were assessed. CHEs (RR: 1.23, 95%CI: 1.19–1.28) were associated with greater mortality risk, and 0.96% mortality was attributable to CHEs. We found that female, the elderly, and people living in north China were more vulnerable to CHEs. In addition, more intensive (RR: 1.07, 95%CI: 1.06–1.08) and consecutive CHEs (RR: 1.09, 95%CI: 1.02–1.17) could increase mortality risk. We further observed a seven to nineteen fold deaths attributable to CHEs in 2090s under middle and high climate change scenarios. Our study found that CHEs significantly increased mortality risk and would cause considerable mortality burden in future. These findings suggest that it is necessary to develop clinical and public health policy to alleviate the mortality burden associated with CHEs.