Bronchiolitis as a possible cause of wheezing in childhood: new evidence.

A historical cohort study was performed in order to assess the hypothesis that even mild bronchiolitis in infancy in a predictor of wheezing later in childhood. Subjects who had experienced bronchiolitis and a matched control group were compared in terms of reported wheezing 8 years later. A highly significant difference was found between the bronchiolitis group and the control group in terms of current wheezing (P less than .0001, relative risk 3.24). This difference was maintained after adjusting for many potentially confounding variables including family history of allergy and other allergic manifestations in the child. Results suggested that 13.6% of a normal practice population in the age range 6 to 9 years currently wheeze, but that 44.1% of children who experienced bronchiolitis currently wheeze. Based on the incidence of bronchiolitis (4.27/100 children in their first 2 years of life) and the relative odds for wheezing derived from a logistic regression model including variables that measured passive smoking, genetic tendency to wheeze, and bronchiolitis, calculations of attributable risk suggested that wheezing in 9.4% of the population of children who currently wheeze was attributable to bronchiolitis.