Abstract

Objective To evaluate trends and geographic distribution of infant bronchiolitis hospitalizations in Chile, a country with large variation in solar radiation (SR) and high rates of urban air pollution. Methods We performed a nationwide ecological study of bronchiolitis hospitalizations from 2001 to 2014. We investigated the associations of regional SR (a proxy of vitamin D status) and regional fine particulate matter (PM2.5) air pollution with bronchiolitis hospitalizations. We also evaluated the role of sociodemographic factors, including regional poverty, education, indigenous population, and rurality rates. Results During the study period, 119 479 infants were hospitalized for bronchiolitis in Chile; 59% were boys. The mean bronchiolitis hospitalization rate increased from 29 to 41 per 1000 infants per year (P = .02). There was an inverse correlation between regional SR and incidence of hospital admissions for bronchiolitis (r = -0.52, P = .049), accounting for 27% of these hospitalizations. There was also a significant direct correlation between regional ambient PM2.5 and bronchiolitis hospitalizations (R = 0.68, P = .006), accounting for 42% of the variation in admission rate. High firewood and/or coal residential use for heating, high regional poverty, lower years of education, and high rurality rates were also significantly correlated with bronchiolitis hospitalization rates. None of the environmental or sociodemographic factors evaluated were correlated with regional case fatality rates or length of stay at the hospital. Conclusions This ecological study revealed significant associations between regional SR, air pollution, and sociodemographic factors with infant bronchiolitis hospitalizations in Chile, suggesting that these factors play a major role in the incidence and severity of respiratory infections in early childhood.