Lung function trajectories and determinants from birth to 6 years in an African birth cohort: extending trajectories through infancy using oscillometry

BACKGROUND: Impaired lung function trajectories in childhood are associated with lifelong health risk. However, data are lacking on trajectories in infancy and preschool years, a time of critical lung growth with potential for interventions. We investigated lung function trajectories from birth through 6 years, and their determinants, in the Drakenstein Child Health study, an African birth cohort. METHODS: Children were followed from birth, with lung function (intra-breath oscillometry) measured at six time points (6 weeks to 6 years). Comprehensive exposure information was longitudinally collected from the antenatal period through childhood. Longitudinal data on end-expiratory resistance and end-expiratory reactance were jointly modelled using group-based multi-trajectory modelling to derive trajectories of respiratory system impedance. RESULTS: 830 children with two or more lung function measures were included. A model comprising five trajectories was the optimal solution: normal (70.2%); persistent low (2.4%); early normal-decline (8.4%); early low-catch-up (5.8%); and decline and recovery (13.1%). 90 children (11%) had low trajectories (persistent low or early normal-decline). Risk factors were respiratory syncytial virus-lower respiratory tract infection, preterm birth and postnatal maternal psychological distress. 157 children (19%) showed catch-up to normal lung function (early low-catch-up or decline and recovery) through 6 years. Spirometry at 6 years differed by trajectory: children in the normal trajectory had the highest forced expiratory volume in 1 s and forced vital capacity, and those in the persistent low trajectory had the lowest. CONCLUSION: Specific early-life lung function trajectories show potential for healthy lung development and recovery in early childhood. Modifiable factors including prematurity, respiratory syncytial virus-lower respiratory tract infection and maternal psychological distress negatively affect lung trajectories.