We previously reported an increased risk for bronchial obstructive disease and allergic sensitization up to age 3 in 47 children hospitalized with a respiratory syncytial virus (RSV) bronchiolitis in infancy compared with 93 matched control subjects recruited during infancy. The aims of the present study were to evaluate the occurrences of bronchial obstructive disease and allergic sensitization in these children at age 7(1)/ (2). All 140 children reported for the follow-up, which included physical examination, skin prick tests, and serum IgE tests for common food and inhaled allergens. The cumulative prevalence of asthma was 30% in the RSV group and 3% in the control group (p < 0.001), and the cumulative prevalence of "any wheezing" was 68% and 34%, respectively (p < 0.001). Asthma during the year prior to follow-up was seen in 23% of the RSV children and 2% in the control subjects (p < 0.001). Allergic sensitization was found in 41% of the RSV children and 22% of the control subjects (p = 0.039). Multivariate evaluation of possible risk factors for asthma and sensitization using a stepwise logistic statistical procedure for all 140 children showed that RSV bronchiolitis had the highest independent risk ratio for asthma (OR: 12.7, 95% CI 3.4 to 47.1) and a significantly elevated independent risk ratio for allergic sensitization (OR: 2.4, 95% CI 1.1 to 5.5). In conclusion, RSV bronchiolitis in infancy severe enough to cause hospitalization was highly associatied with the development of asthma and allergic sensitization up to age 7(1)/ (2). The results support the theory that the RSV influences the mechanisms involved in the development of asthma and allergy in children.

We have prospectively studied wheezing disorder and allergy in 47 children hospitalized with respiratory syncytial virus (RSV) bronchiolitis in infancy and 93 matched control subjects. Subjects with at least three episodes of wheezing were defined as recurrent wheezers and as having asthma if the episodes were doctor verified. Here we report the outcome at age 13 years in 46/47 children with RSV and 92/93 control subjects. Wheezing disorder and clinical allergy were estimated using a questionnaire. Skin prick tests were performed and serum IgE antibodies measured. Spirometry was undertaken at rest, after dry air challenge, and after beta2-agonist inhalation. The occurrence of symptoms over the previous 12 months was significantly higher in the RSV group than among the control subjects, 43% versus 8% for asthma/recurrent wheezing and 39% versus 15% for allergic rhinoconjunctivitis. Sensitization to common inhaled allergens was more frequent in the RSV group than in the control subjects, judged by skin prick tests (50% versus 28%; p = 0.022), or by serum IgE antibodies (45% versus 26%; p = 0.038). Compared with the control subjects, the RSV group showed mild airway obstruction both at rest and after bronchodilation, and had slightly more reactive airways. RSV bronchiolitis in infancy severe enough to cause hospitalization is a risk factor for allergic asthma in early adolescence.

Background An increased prevalence of asthma/ recurrent wheeze (RW), clinical allergy and allergic sensitisation up to age 13 years has previously been reported in subjects hospitalised with respiratory syncytial virus (RSV) bronchiolitis in their first year of life compared with matched controls. A study was undertaken to examine whether these features persist into early adulthood, to report longitudinal wheeze and allergy patterns, and to see how large and small airway function relates to RSV infection and asthma. Methods Follow-up at age 18 years was performed in 46 of 47 subjects with RSV and 92 of 93 controls. Assessments included questionnaire, clinical examination, skin prick tests, serum IgE antibodies to inhaled allergens, blood eosinophils, fraction of exhaled nitric oxide (FeNO), spirometry, multiple breath washout (lung clearance index, LCI) and dry air hyperventilation challenge. Results Increased prevalence of asthma/RW (39% vs 9%), clinical allergy (43% vs 17%) and sensitisation to perennial allergens (41% vs 14%) were present at age 18 in the RSV cohort compared with controls. Persistent/ relapsing wheeze associated with early allergic sensitisation predominated in the RSV cohort compared with controls (30% vs 1%). Spirometric function was reduced in subjects with RSV with or without current asthma, but not in asthmatic controls. LCI was linked only to current asthma, airway hyperresponsiveness and FeNO. Conclusions Severe early RSV bronchiolitis is associated with an increased prevalence of allergic asthma persisting into early adulthood. Small airway dysfunction (LCI) is related to current asthma and airway inflammation but not to RSV bronchiolitis. Reduced spirometry after RSV may reflect airway remodelling.

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