Viral Bronchiolitis and Asthma Development: Lessons from Longitudinal Studies

Currently, two birth cohort studies with a focus on on early-life wheezing available have continued until adulthood. At 22 years of age, about a third of early life wheezers had asthma, and another third was in remission though having wheezed at teen age. There are four prospective post-bronchiolitis follow-up studies continued from infancy until teenage or longer, two from Finland and two from Sweden. The prevalence of doctor-diagnosed asthma at 13-15 years of age varied from 13% to 40% in these four studies. The prevalence at 17-20 years of age was surprisingly similar, 41-43%, in those two studies which continued until that age. The Finnish cohort was examined again at 26-29 years of age, and doctor-diagnosed asthma was present in 41% vs 10% in population controls. Parental asthma, sensitization to inhaled allergens, eosinophil activity, passive smoking in infancy and recurrent wheezing at <24 months of age, as well as non- RSV, especially rhinovirus etiology of early-life wheezing, were the significant infantile risk factors for asthma at 13-20 years of age. The post-bronchiolitis lung function studies have offered preliminary evidence that RSV bronchiolitis may be associated with later non-reversible obstructive or even restrictive pulmonary disorder, whereas rhinovirus bronchiolitis was associated with with reversible, obstructive pulmonary disorder.