Background Previous studies found that high temperature and heatwave increase the risk of traffic injuries. The complex road conditions in Yunnan Province result in frequent traffic accidents. However, there is limited evidence on the correlation between heatwave and traffic injuries in Yunnan Province.

Objective To assess the association between heatwave events and traffic injuries, to estimate its disease burden, and to identify relevant sensitive groups.

Methods We collected data on traffic injury cases and concurrent meteorological information from four surveillance sites in Yunnan Province, China: Dali, Lufeng, Zhaoyang, and Qilin from May to September each year from 2015 to 2023. Traffic injury cases refer to patients who visited the outpatient or emergency departments of local surveillance hospitals for the first time due to traffic injuries. Meteorological data were derived from the fifth generation atmosphericreanalysis dataset of the global climate provided by the European Centre for Medium-Range Weather Forecasts. A time-stratified case-crossover design combined with distributed lag non-linear model was used to analyze the association between short-term exposure to heatwave and traffic injuries. We also conducted subgroup analyses by sex, age, occupation, injury cause, activity at the time of injury occurrence, and severity of injury.

Results A total of 34764 traffic injury surveillance cases were included in the analysis. The risk of traffic injuries occurred during heatwave was 1.13 times (95%CI: 1.07, 1.20) greater than those occurred during non-heatwave, and 2.64% (95%CI: 1.49%, 3.73%) of traffic injuries were attributed to heatwave exposure throughout the study period. The results of stratified analysis showed greater impacts of heatwave on the risk of traffic injuries in female odds ratio (OR)=1.17, attributable fraction (AF)=3.23%, people aged 15-64 years (OR=1.13, AF=2.68%), farmers/workers (OR=1.22, AF=4.07%), people with non-motor vehicle traffic injuries (OR=1.17, AF=3.24%), people who were driving or riding when injuries occurred (OR=1.12, AF=2.43%), and people with minor injuries (OR=1.18, AF=3.49%) ( P<0.05). Longer duration excess risk (ER)=0.99% and greater intensity (ER=4.12%) of heatwave had greater impacts on the risk of traffic injuries (P<0.05).

Conclusion Heatwave events are associated with an increased risk of traffic injuries. Female, people aged 15-64, farmers/workers, people with non-motor vehicle traffic injuries, those injured while driving/riding a vehicle, and people with minor injuries are particularly vulnerable. The findings suggest that targeted mitigation and adaptation measures should be taken to address the risk of traffic injuries associated with extreme climate events.