Association between short-term heat exposure and herpangina incidence in Japan: a nationwide space-time-stratified case-crossover study

This study aims to quantify the impact of ambient temperature on the risk of herpangina in Japan. We compiled weekly time-series data on the incidence of herpangina and meteorological factors in all 47 Japanese prefectures (2005-2019). A space-time-stratified case-crossover design, combined with a distributed lag nonlinear model, was employed to estimate the relative risk (RR) of heat exposure across prefectures. A multivariate meta-analysis was conducted to obtain pooled estimates at the national level. Our analysis revealed a nonlinear, inverted U-shaped association between ambient temperature and the incidence of herpangina at the national level in Japan. Peak risk occurred at 24.3 °C, with an RR of 8.65 (95% confidence interval: 6.32-11.84) relative to the minimal risk. This association was predominantly driven by the immediate effects of high temperatures, with the risk persisting for up to four weeks. Our assessment demonstrates that high temperatures increase the risk of herpangina, highlighting the need for targeted preventive measures to mitigate the health impacts of global warming.