Bronchiolitis, regardless of its aetiology and severity, is associated with an increased risk of asthma: a population-based study.

An association exists between severe Respiratory Syncytial Virus (RSV)-bronchiolitis and a subsequent increased risk of recurrent wheezing (RW) and asthma. However, a causal relationship remains unproven. Using a retrospective population-based cohort study (339,814 children), bronchiolitis during the first two years (regardless of aetiology and severity) was associated with at least a threefold increased risk of RW/asthma at 2-4 years and an increased prevalence of asthma at ≥5 years of age. The risk was similar in children with mild bronchiolitis as in those with hospitalised-RSV-bronchiolitis and was higher in children with hospitalized-non-RSV-bronchiolitis. The rate of RW/asthma was higher when bronchiolitis occurred after the first 6 months of life. Our results seem to support the hypothesis of a shared predisposition to bronchiolitis (irrespective of aetiology) and RW/asthma. However, 60% of hospitalized bronchiolitis in our setting are due to RSV, which should be paramount in decision-making on imminent RSV prevention strategies.