Air Pollution Interacts With Past Episodes of Bronchiolitis in the Development of Asthma

Abstract

To evaluate whether air pollution affects the development of asthma in children with previous episodes of bronchiolitis.A total of 1743 children, with a mean age of 6.83 years, were included in this study. Children were recruited from 16 elementary schools in 7 cities throughout Korea. A total of 1340 of these children were followed up 2 years later.All children had parental completion of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and an allergy evaluation consisting of pulmonary function tests, skin-prick testing, and a methacholine challenge at the time of enrollment. Air pollution was calculated as an average of the concentrations of ozone, carbon monoxide, nitric dioxide, sulfur dioxide, and particulate matter <10 μm in diameter between 2001 and 2005, based on a geographic sampling system.Higher exposure to ozone and carbon monoxide was associated with airway hyperresponsiveness at the time of enrollment. Previous episodes of bronchiolitis increased the child’s risk of both current wheezing and physician-diagnosed asthma. When the 2 factors were combined, the risk of airway hyperresponsiveness, wheezing, physician-diagnosed asthma, and decreased pulmonary function test results was higher.In children, those who had both a history of bronchiolitis and exposure to higher amounts of air pollution were found to have a higher prevalence of asthma, heightened bronchial reactivity, and decreased lung function compared with children without these exposures.This study is novel in that it is the first to reveal an apparently synergistic effect between bronchiolitis and air pollution on the development of asthma in children. Further research is needed into the mechanisms of this synergy, as well as possible targets for intervention, to prevent the development of asthma in this high-risk population.