Ambient Air Pollution and Kawasaki Disease: A Systematic Review and Meta‐Analysis of Epidemiological Evidence

Background Kawasaki disease (KD) is a childhood vasculitis with a multifactorial etiology involving genetic susceptibility and environmental influences. Ambient air pollution has been proposed as a potential environmental trigger, but epidemiological findings have been inconsistent across pollutants, populations, and exposure periods. This systematic review and meta‐analysis aimed to synthesize the association between ambient air pollution and KD. Methods PubMed, Embase, and Web of Science were searched from database inception through December 29, 2024, for observational studies evaluating associations between ambient air pollutants and KD. Multivariable‐adjusted estimates were preferentially used for quantitative synthesis. Hazard ratios and odds ratios were interpreted as relative risks, and estimates were standardized to a 10 µg/m 3 increase in pollutant concentration where applicable. Random‐effects models were used to obtain pooled relative risks, with heterogeneity assessed using I 2 statistics. Results Thirteen studies met the inclusion criteria. The studies included diverse epidemiological designs and were predominantly conducted in Asian populations, with additional studies from North America and Italy. Across the quantitative synthesis, no statistically significant association was observed between a standardized 10 µg/m 3 increase in individual pollutants and KD occurrence. The pooled relative risks were 1.00 (95% confidence interval [CI], 0.985–1.016) for PM 2.5 , 1.00 (95% CI, 0.983–1.022) for PM 10 , 1.008 (95% CI, 0.966–1.051) for SO 2 , 0.99 (95% CI, 0.989–1.009) for NO 2 , and 1.013 (95% CI, 0.981–1.046) for O 3 and CO. For PM 2.5 , between‐study heterogeneity was moderate ( I 2 = 43.8%), whereas Egger's test showed no evidence of significant publication bias ( p = 0.2703). Conclusion Current evidence does not demonstrate a statistically significant overall association between ambient air pollution and KD. However, associations may vary by pollutant, exposure timing, geographical setting, and meteorological conditions. Future studies should use standardized exposure windows and account for key meteorological factors to clarify these potential context‐specific associations.