Epidemiological characteristics of heatstroke in China, 2010-2023: a longitudinal study based on a national heatstroke surveillance system.

Background: Heatstroke causes numerous pathophysiological changes and can lead to death. Extreme heat events have been increasing in frequency, duration, and intensity worldwide in recent decades and are causing growing public health concern. However, epidemiological studies of heatstroke are limited in number and scope, and have had relatively small sample sizes. To better understand the epidemiological characteristics of heatstroke and advance evidence-based prevention and control strategies, we conducted an observational study of reported heatstroke cases in China. Methods: Cases included in this study were patients clinically diagnosed with heatstroke during the study period of 2010-2023, reported through a dedicated heatstroke surveillance system established by China CDC. We used descriptive statistical methods to determine the epidemiological characteristics of heatstroke in China. Findings: There were 86,406 heatstroke cases reported during the study period, with an increasing reporting trend (Spearman correlation coefficient r = 0·79). Annual incidence (Spearman r = 0·77) and proportion of severe cases (Pearson r = 0·67) were positively correlated with the number of nationwide average annual high-temperature days. The overall incidence was 44·83 per 10 million person-years, and the mortality rate was 0·89 per 10 million person-years; 32·02% of cases were severe; the overall case fatality rate (CFR) was 1·98%, and the CFR for severe cases was 6·19%. Most cases and deaths were reported in summer, with peaks in late July. The peaks of incidence, duration, and severity varied by region. The mean age was (50·46 ± 18·73) years, with male cases younger than female cases (49·21 ± 17·41 vs 53·60 ± 21·36; t = -28·73, p < 0·0001). For every five-year increase in age, the risks of severe heatstroke and death increased by 14·64% (95% CI: 1·1415-1·1513) and 25·76% (CI: 1·2400-1·2755), respectively. The male:female ratio was 2·49:1; males exhibited a higher risk of suffering from heatstroke and having greater disease severity than females. Interpretation: Our study provides a clear profile of heatstroke cases, and highlights differences by population, region, and time of year. Results inform formulation of evidence-based strategies for enhanced heatstroke preparedness and response, such as enhancing public health early warning systems, prioritizing protection for vulnerable groups, and advancing localized interventions for risk communication and clinical management. Funding: Public Health Talent Program of China's National Disease Control and Prevention Administration.