Airway bacterial carriage and childhood respiratory health: A population‐based prospective cohort study

BACKGROUND: Airway bacterial carriage might play a role in respiratory disease. We hypothesize that nasal carriage with Staphylococcus aureus or nasopharyngeal carriage with Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae predisposes individuals to adverse respiratory health. OBJECTIVE: To examine the association of early‐life airway bacterial carriage with respiratory tract infections and vice versa, and of early‐life airway bacterial carriage with wheezing, lung function, and asthma in later childhood. METHODS: We collected upper airway swabs for bacterial culturing for S aureus, H influenzae, M catarrhalis, and H influenzae at six timepoints between the ages of 6 weeks and 6 years among 945 children participating in a population‐based prospective cohort study. Information on respiratory tract infections and wheezing until age 6 years, and asthma at age 10 years was obtained by questionnaires. Lung function at age 10 years was measured by spirometry. We tested possible bidirectional associations between airway bacterial carriage and respiratory tract infections by cross‐lagged models, and associations of repeatedly measured airway bacterial carriage with wheezing, lung function, and asthma by generalized estimating equations models and regression models. RESULTS: Cross‐lagged modeling showed that early‐life airway bacterial carriage was not consistently associated with upper and lower respiratory tract infections or vice versa. Nasopharyngeal carriage with any bacteria in infancy was associated with an increased risk of wheezing (OR [95% CI]: 1.66 [1.31, 2.10]). Airway bacterial carriage was not consistently associated with school‐age lung function or asthma. CONCLUSION: Nasopharyngeal carriage with any bacteria is associated with wheezing, but not respiratory tract infections, asthma, or lung function.