National mortality burden attributable to the unprecedented heatwave in 2022 in China.

Abstract

Background: In 2022, China experienced an unprecedented heatwave event, raising concerns about the health impacts of heatwaves. This study aims to understand the devastating health risk of the exceptional heatwave in 2022 by comparing heatwave-related mortality burden in 2022 with that during 2000-2021.

Methods: We collected daily mortality and daily maximum temperature (DMT) during 2006-2017 in 364 locations (counties/districts) of China. Heatwave was defined as an event with 2 or more consecutive days of DMT exceeding the 92.5th percentile. We employed a distributed lag nonlinear model (DLNM) and a meta-analysis to examine the heatwave-mortality association based on the data from 364 counties/districts, and then this association was used to assess the mortality burden attributable to heatwaves during 2000-2022 in 368 cities in China. A percentage change (%) indicator, comparing the 2022 mortality burden to the average value from 2000 to 2021, was further calculated to highlight the severity of heatwaves in 2022.

Results: In the past 2 decades, the frequency and intensity of heatwaves in China significantly increased, with the cumulative excessive degree-day increasing to 31,626 in 2022 compared with the annual average value of 13,772 during 2000-2021 across China. In 2022, we observed 62,961 [95% confidence internal (CI) 54,945-70,413] heatwave-related deaths in China, which was much higher than the annual average [35,987 (95% CI 31,252-40,471)] attributable to heatwaves during 2000-2021. The vulnerability groups of heatwave-related mortality in 2022 primarily included patients with cardiovascular diseases [40,567 (95% CI 35,313-45,404)], females [35,876 (95% CI 31,035-41,005)], and people aged over 65 years [56,208 (95% CI 49,023-62,864)]; and greater heatwave-related mortality was found in eastern-central China. The attributable fraction (AF) of heatwave-related deaths increased from an annual average of 11.01‰ (95% CI 9.56-12.38) during 2000-2021 to 18.11‰ (95% CI 15.80-20.25) in 2022 with 64.43% increment (95% CI 38.10-93.78), and the increase rates were greater in Xizang Autonomous Region (159.77%, 95% CI 12.84-477.87) and Sichuan Province (133.64%, 95% CI 3.84-416.61).

Conclusions: This study indicated that the frequency and intensity of heatwaves significantly increased in the past 2 decades in China, and the 2022 heatwaves were linked to a substantial mortality burden in China, with significant population and regional heterogeneity. Our findings underscore the need for developing comprehensive heat adaptation plans in the context of rapid aging and ongoing global warming.