Household-specific indoor PM2.5 and PM10-2.5 concentrations and Kawasaki disease onset by age six: the Japan Environment and Children's Study.

BACKGROUND: Onset of Kawasaki disease has been linked to atmospheric dust and various everyday environmental exposures, including immune stimulation; however, its association with household-specific indoor particulate matter (PM) concentrations remains unclear. Therefore, we examined the associations of indoor PM2.5 and PM10-2.5 concentrations with the onset of Kawasaki disease by 6 years of age. METHODS: We analyzed 3846 mother-child pairs from the Sub-Cohort Study of the Japan Environment and Children's Study. Indoor PM2.5 and PM10-2.5 concentrations were measured over 1-week periods at ages 1.5 and 3.0 years, log-transformed to address their skewed distributions, and then averaged. The outcome was onset of Kawasaki disease by 6 years of age. Logistic regression models were used to estimate odds ratios across exposure categories, and generalized additive models assessed nonlinear associations, adjusted for a priori selected potential confounders. RESULTS: The cumulative incidence of Kawasaki disease by 6 years of age was 15.34 per 1000. Intraclass correlation coefficients for averaged log-transformed indoor PM2.5 and PM10-2.5 concentrations at 1.5 and 3.0 years of age were 0.52 and 0.55, respectively. Higher PM10-2.5 concentrations were associated with lower odds ratios of Kawasaki disease, with a consistent inverse pattern across exposure levels. A similar consistent trend was observed for PM2.5, although it was weaker than that for PM10-2.5. CONCLUSIONS: Higher household-specific indoor PM concentrations, particularly PM10-2.5, were associated with a lower risk of Kawasaki disease onset by 6 years of age. Further in-depth studies with larger sample sizes are needed.