Early Respiratory Infections and the Development of Asthma in the First 27 Years of Life.

Previous studies have provided contradictory evidence on the role of early childhood respiratory infections in the development of asthma and other allergic diseases during childhood. We investigated early-life respiratory infections as predictors of the development of asthma in a 20-year prospective cohort study (the Espoo Cohort Study, 1991-2011). Information on upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs) was collected with a parent-administered baseline questionnaire covering the preceding 12 months (part 1; n = 2,228), and information on LRTIs leading to hospitalization was obtained from the National Hospital Discharge Registry (part 2; n = 2,568). The incidence of asthma was assessed on the basis of 6-year and 20-year follow-up questionnaires. Adjusted hazard ratios were estimated using Cox proportional hazards models. Both URTIs (adjusted hazard ratio (HR) = 1.64, 95% confidence interval (CI): 1.22, 2.19) and LRTIs (adjusted HR = 2.11, 95% CI: 1.48, 3.00) in early childhood were strong predictors of asthma incidence up to young adulthood (ages 20-27 years). A declining age trend was present for both URTIs (P-trend < 0.01) and LRTIs (P-trend < 0.001). In part 2 of our analysis, a significant risk of asthma was found in relation to LRTIs requiring hospitalization (adjusted HR = 1.93, 95% CI: 1.10, 3.38). The results provide new evidence that respiratory tract infections in early life predict the development of asthma through childhood to young adulthood.