Cause-specific accidental deaths and burdens related to ambient heat in a warming climate: A nationwide study of China

Future warming is projected to increase the heat-related mortality burden, especially for vulnerable populations. However, most previous studies focused on non-accidental morbidity or mortality, with far less research on heat-related accidental events.We collected individual accidental death records among all residents in Chinese mainland from June to August during 2013-2019. Accidental deaths were further divided into several subtypes by different causes. We used an individual-level, time-stratified, case-crossover study design to estimate the association between daily mean temperature and accidental deaths, and estimate its variation in seven geo-climatic zones, age (5-64, 65-74, ≥75), and sex (male, female). We then estimated the temperature-related excess accidental deaths under global warming scenarios of 1.5, 2, and 3℃.A total of 711,929 accidental death records were included in our study. We found that higher temperatures were associated with increased risks of deaths from the total accidental events and four main subtypes, including traffic, falls, drowning, and unintentional injuries. We also found that younger individuals (ages 5-64) and males faced a higher risk of heat-related mortality due to total accidents, traffic incidents, and drowning. For future climate scenarios, even under the 1.5℃ climate change scenario, 6,939 (95% eCI (empirical Confidence Interval): 6,818-7,067) excess accidental deaths per year are attributed to higher summertime daily temperature over mainland China, and the number of accidental deaths would increase by 16.71% and 33.59% under the 2℃ and 3℃ climate change scenarios, respectively. For residents living in southern coastal and northwest inland regions, the projected increase in accidental death is higher.This nationwide study confirms that higher summer temperatures are linked to an increased risk of accidental deaths. Younger age groups and males face a higher risk. This indicates that current estimates of the health effects of climate change might be underestimated, particularly for younger populations.