A population-based prospective cohort study examining the influence of early-life respiratory tract infections on school-age lung function and asthma

Background Early-life respiratory tract infections could affect airway obstruction and increase asthma risk in later life. However, results from previous studies are inconsistent.
Objective We examined the associations of early-life respiratory tract infections with lung function and asthma in school-aged children.
Methods This study among 5197 children born between April 2002 and January 2006 was embedded in a population-based prospective cohort study. Information on physician-attended upper and lower respiratory tract infections until age 6 years (categorised into ≤ 3 and >3-6 years) was obtained by annual questionnaires. Spirometry measures and physician-diagnosed asthma were assessed at age 10 years.
Results Upper respiratory tract infections were not associated with adverse respiratory outcomes. Compared with children without lower respiratory tract infections ≤3 years, children with lower respiratory tract infections ≤3 years had a lower FEV 1, FVC, FEV 1:FVC and forced expiratory flow at 75% of FVC (FEF 75) (Z-score (95% CI): ranging from -0.22 ( -0.31 to -0.12) to -0.12 ( -0.21 to -0.03)) and an increased risk of asthma (OR (95% CI): 1.79 (1.19 to 2.59)). Children with lower respiratory tract infections >3-6 years had an increased risk of asthma (3.53 (2.37 to 5.17)) only. Results were not mediated by antibiotic or paracetamol use and not modified by inhalant allergic sensitisation. Cross-lagged modelling showed that results were not bidirectional and independent of preschool wheezing patterns.
Conclusion Early-life lower respiratory tract infections ≤3 years are most consistently associated with lower lung function and increased risk of asthma in school-aged children.