In this African birth cohort study, lung function trajectories were tracked from birth to 6 years using intra-breath oscillometry to quantify end-expiratory impedance components. Six measurement points (6 weeks to 6 years) enabled joint modelling of end-expiratory resistance and reactance, yielding five distinct respiratory-system-impedance trajectories: normal (70.2%), persistent low (2.4%), early normal with decline (8.4%), early low with catch-up (5.8%), and decline with recovery (13.1%). Overall, 11% (90/830) exhibited low trajectories (persistent low or early normal with decline) through age 6. Early-life factors associated with adverse trajectories included respiratory syncytial virus lower respiratory tract infection, prematurity, and postnatal maternal psychological distress. Conversely, about 19% (157) demonstrated catch-up to normal function by age 6, via early low with catch-up or decline and recovery trajectories. At 6 years, spirometric indices varied by trajectory, with the normal group showing the highest FEV1 and FVC, and the persistent low group the lowest. The study notes uncertainty remains regarding the full causal impact of modifiable factors and the extent to which these trajectories reflect true lung development versus measurement or population-specific effects.
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.