Background Early life factors impact long-term respiratory health. Better understanding lung development is essential to strengthen respiratory health across the life course

Aim Assess the impact of early life factors on lung function trajectories from birth to 5yrs 

Methods We prospectively followed mothers and their offspring antenatally through 5 yrs in a South African birth cohort. Lung function: oscillometry (OS), tidal breathing (TBFVL), multiple breath washout (MBW) was measured at 6 wks and annually 1-5 yrs, providing 6 time points. Comprehensive longitudinal measures of exposures including aetiology of lower respiratory tract illness (LRTI) were done.  The impact of early life factors on height-adjusted lung function trajectories was explored 

Results 966 children were followed for 4830 child yrs; 49% female, 15% preterm, 22% HIV exposed uninfected (HEU), 88% household income <?265/mth, 30% mothers smoked. 440(46%) children had an LRTI during 5 yrs: 162(17%) RSV-LRTI. 9816 lung function measures (3034 OS, 3034 TBFVL, 3748 MBW) were used for lung function trajectories. Each LRTI impacted lung growth trajectories [coef, 95%CI; p-value]: lower compliance (C) [0.95, 0.92-0.98; <0.01]; if RSV-LRTI: FRC: 1.06, 1.03-1.1;<0.01; tPTEF/tE: 0.93, 0.89-0.97;<0.01; prematurity increased resistance (R) [1.05, 1.03-1.07; <0.001]; reduced C [0.92, 0.89-0.94; <0.001] and tidal volume [0.98, 0.97-0.99; =0.002]; HEU had increased LCI [1.01,1.00-1.02; =0.002]; smoke exposed had higher R [1.02, 1.01-1.04; <0.001]; children from poorer households had lower trajectories

Conclusions Novel insights into the impact of early life factors on lung development were identified, highlighting areas for prevention