Ambient Temperature and Kawasaki Disease in Seoul, Korea: Evidence from Nationwide HIRA Data Using Case-Crossover and Time-Series Analyses

Abstract Background Kawasaki disease (KD) is an acute vasculitis of childhood and the leading cause of acquired heart disease in developed countries. The impact of ambient temperature on KD incidence remains unclear. We analyzed nationwide claims data for children aged 0–9 years in Seoul between 2012 and 2019. Associations between ambient temperature and KD were examined using a time-stratified case-crossover design and quasi-Poisson time-series regression within a distributed lag non-linear model framework (lags up to 21 days). Reduced-basis models summarized cumulative effects, and analyses were stratified by age. A total of 28,866 KD cases were identified. In the case-crossover analysis, the cumulative effect over lag 0–21 days was not significant. However, at lag 14–21 days, risk increased relatively linearly above 25°C, with an OR of 1.13 (95% CI: 1.03–1.23) at 29.7°C (97.5th percentile) compared with 25°C, while no significant decrease was observed at − 6.9°C (2.5th percentile). In the time-series analysis, risk decreased below 25°C and increased above 25°C over lag 0–21 days, with a more pronounced cumulative effect at lag 14–21 days (RR 1.14, 95% CI: 1.05–1.25 at 29.7°C). Age-stratified analyses showed consistent results in children aged 1–4 years, while associations were less clear in < 1 and 5–9 years. High ambient temperatures were associated with a delayed increase in KD risk, particularly among children aged 1–4 years, highlighting the potential influence of climate change on pediatric health.