Respiratory syncytial virus in early life and risk of wheeze and allergy by age 13 years

Background The relation between lower respiratory tract illnesses in early life caused by the respiratory syncytial virus (RSV) and the subsequent dev elopment of wheezing acid atopy in childhood is not well understood. We stu died this relation in children who had lower respiratory tract illnesses th at occurred before 3 years of age. Methods Children were enrolled at birth and cases of lower respiratory trac t illness were ascertained by a physician. Viral tests were done for specim ens collected at the time of the illness. Children were classified into fiv e groups according to type and cause of lower respiratory tract illness. Ch ildren were then followed prospectively up to age 13, and we measured frequ ency of wheezing, pulmonary function, and atopic status (allergy skin-prick tests, serum IgE concentrations). Findings RSV lower respiratory tract illnesses were associated with an incr eased risk of infrequent wheeze (odds ratio 3.2 [95% CI 2.0-5.0], p<0.001), and an increased risk of frequent wheeze (4.3 [2.2-8.7], p less than or eq ual to 0.001) by age 6, Risk decreased markedly with age and was not signif icant by age 13. There was no association between RSV lower respiratory tra ct illnesses and subsequent atopic status. RSV lower respiratory tract illn esses were associated with significantly lower measurements of forced expir atory volume (2.11 [2.05-2.15], p less than or equal to 0.001) when compare d with those of children with no lower respiratory tract illnesses, but the re was no difference in forced expiratory volume after inhalation of salbut amol. Interpretation RSV lower respiratory tract illnesses in early childhood are an independent risk factor for the subsequent development of wheezing up t o age 11 years but not at ape 13. This association is not caused by an incr eased risk of allergic sensitisation.