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 from 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 timepoints (six-weeks to six-years). Comprehensive exposure information was longitudinally collected from the antenatal period through childhood. Longitudinal data on resistance (Ree) and reactance at end expiration (Xee) were jointly modelled using Group-based multi-trajectory modelling to derive trajectories of respiratory system impedance. Findings 830 children with ≥two lung function measures were included. A model comprising 5-trajectories was the optimal solution: Normal (70.2%); Persistent low (2.4%); Early normal-declines (8.4%); Early low-catch up (5.8%); Decline and recovery (13.1%). Ninety (11%) children 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. One hundred and fifty seven children (19%) showed catch-up to normal lung function (Early low-catch-up or Decline and recovery) through six years. Spirometry at 6-years differed by trajectory: children in the Normal trajectory had the highest FEV 1 and FVC, and those in the Persistent low, the lowest. Interpretation Specific early life lung function trajectories show potential for healthy lung development and recovery in early childhood. Modifiable factors including prematurity, RSV-LRTI and maternal psychological distress negatively impact on lung trajectories.