Weather condition, air pollutants, and epidemics as factors that potentially influence the development of Kawasaki disease.

Environmental factors have been suspected to have effects on the development of Kawasaki disease. However, the associations have been conflicting. The aim of this study was to investigate the effects of air pollution, weather conditions, and epidemic infections on the risks for Kawasaki disease in Japan. The concentrations of air pollutants (nitric oxide, nitrogen dioxide, and sulfur dioxide); ambient weather conditions (temperature, atmospheric pressure, relative air humidity, precipitation, sunshine duration, and wind velocity); and the epidemic conditions of 14 infectious diseases in hospitalized patients with Kawasaki disease were monitored from 2011 to 2018 in Beppu, Japan. The overdispersed generalized additive model was used to evaluate the effects, and a combination model with a distributed lag nonlinear model was used to estimate the cumulative effects. The incidence of Kawasaki disease had positive associations with preceding hot temperature and increased concentrations of nitric oxide and sulfur dioxide and a negative association with epidemic herpangina. The cumulative relative risk of Kawasaki disease at 5 lagged days of increased temperature was 1.76 (95% confidence interval: 1.01-3.07). This city-level observational study suggested that the incidence of Kawasaki disease was associated with air pollution and increased temperature and may be indirectly influenced by epidemic herpangina.