Risk factors for irreversible airway obstruction after infant bronchiolitis

Background: Increasing evidence shows that environmental factors in childhood play a role in development of irreversible airway obstruction. We evaluated early-life and preschool-age risk factors for irreversible airway obstruction in adolescence after bronchiolitis in infancy. Methods: This study is a secondary analysis of data collected during prospective long-term follow-up of our post-bronchiolitis cohort. Risk factor data were collected during hospitalisation and on follow-up visits at 5–7 and 10–13 years of ages. Lung function was measured from 103 participants with impulse oscillometry at 5–7 years of age and from 89 participants with flow-volume spirometry at 10–13 years of age. Results: Asthma diagnosis at <12 months of age showed a significant association with irreversible airway obstruction at 10–13 years of age independently from current asthma. Irreversible airway obstruction was less frequent in children with variant than wild genotype of the Toll-like receptor 4 (TLR4) rs4986790, but the significance was lost in logistic regression adjusted for current asthma and weight status. Higher post-bronchodilator respiratory system resistance at 5 Hz and lower baseline and post-bronchodilator reactance at 5 Hz by impulse oscillometry at 5–7 years of age were associated with irreversible airway obstruction at 10–13 years of age. Conclusion: Asthma diagnosis during the first living year and worse lung function at preschool age increased the risk for irreversible airway obstruction at 10–13 years of age after bronchiolitis. TLR4 rs4986790 polymorphism may be protective for development of irreversible airway obstruction after bronchiolitis.