Early-life respiratory tract infections and the risk of school-age lower lung function and asthma: a meta-analysis of 150 000 European children

Background: Early-life respiratory tract infections might affect chronic obstructive respiratory diseases, but conclusive studies from general populations are lacking. Objective: To examine if children with early-life respiratory tract infections had increased risks of lower lung function and asthma at school-age. Methods: We used individual-participant data of 150 090 children primarily from the EU Child Cohort Network to examine the associations of upper and lower respiratory tract infections from age 6 months to 5 years with forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, forced expiratory flow at 75% of FVC (FEF75), and asthma at a median age of 7 (range 4 to 15) years. Results: Children with early-life lower, not upper, respiratory tract infections had a lower school-age FEV1, FEV1/FVC and FEF75 (Z-score (95% CI): ranging from -0.09 (-0.14, -0.04) to -0.30 (-0.36, -0.24)). Children with early-life lower respiratory tract infections had a higher increased risk of school-age asthma than those with upper respiratory tract infections (OR (95%CI): ranging from 2.10 (1.98, 2.22) to 6.30 (5.64, 7.04)), and from 1.25 (1.18, 1.32) to 1.55 (1.47, 1.65)), respectively). Adjustment for preceding respiratory tract infections slightly decreased the strength of the effects. Observed associations were similar for those with and without early-life wheezing as proxy for early-life asthma. Conclusion: Our findings suggest that early-life respiratory tract infections affect development of chronic obstructive respiratory diseases in later life, with the strongest effects for lower upper respiratory tract infections.