The burden of heat-related stroke mortality under climate change scenarios in 22 East Asian cities

Background: Stroke is a leading cause of death and disability in East Asia. Owing to the aging population and high prevalence of stroke, East Asia might suffer a disproportionately heavy burden of stroke under the changing climate. However, the evidence relevant is still limited in this area. Objective: To evaluate the stroke mortality risk due to heat exposure in East Asia and predict its burden under various future climate change scenarios. Methods: We conducted a multi-center observational study and collected data from 22 representative cities in three main East Asian countries (i.e., China, Japan, and South Korea) from 1972 to 2015. The two-stage time-series analyses were applied to estimate the effects of heat on stroke mortality at the regional and country level. We further projected the burden of heat-related stroke mortality using 10 global climate models (GCMs) under four shared socioeconomic pathway and representative concentration pathway (SSP–RCP) scenarios, including SSP1–RCP1.9, SSP1–RCP2.6, SSP2–RCP4.5, and SSP5–RCP8.5 scenarios. Results: In the present study, a total of 287,579 stroke deaths were collected during the warm season. Heat was significantly associated with an increased risk of stroke mortality. Overall, compared with the 2010 s, the heat-related attributable fraction (AF) was projected to increase in the 2090 s, with increments ranging from 0.8 % to 7.5 % across various climate change scenarios. The heat-related AF was projected to reach 11.9 % (95 % empirical confidence interval [eCI]: 6.1 %, 17.5 %) in the 2090 s under the SSP5–RCP8.5 scenario in China, while the corresponding estimates were 6.6 % (95 % eCI: 2.5 %, 11.0 %) and 5.1 % (95 % eCI: 1.2 %, 9.1 %) for Japan and South Korea, respectively. Conclusions: Climate change will exacerbate the burden of heat-related stroke mortality but with considerable geographical heterogeneity in East Asia.