Infant lower respiratory tract illness reduces lung function at 2 years in African children

Background: Lower respiratory tract illness (LRTI) in infancy reduces lung function at 1 year, independent of baseline lung function. Aim: To assess whether the impact of LRTI in infancy on lung function persists to 2 years. Methods: Lung function was measured using tidal breathing, multiple breath washout and the forced oscillation technique at 6 weeks, 1 and 2 years, in a South African birth cohort (Drakenstein Child Health Study). Study staff confirmed LRTI. The association between LRTI and lung function during 2 years was assessed using mixed effect models with random subject effects, adjusted for age, BMI for age Z-score, sex, ethnicity, SES quartile at birth and gestational age. Results: 858 infants (male 52%, HIV exposed 21%, Black African: 52.5%, maternal smoking 33%) were tested at six weeks; 632 (74%) at one and 620 (72%) at two years. 475 children had 872 episodes of LRTI during 2 years. Children who had an LRTI had a higher respiratory rate (RR 4 % change, CI 0.01, 0.05; p=0.002) and lung clearance index (LCI 0.05, CI 0.00, 0.10; p=0.046) and a lower tidal volume (TV -1.5mL, CI-2.9,-0.2; p=0.03) and compliance (-0.49 mL.hPa-1, CI -0.9,-0.04; p=0.03) at 2 years vs. those without LRTI. The effect was stronger with each further LRTI episode (RR further 1% increase, p=002; TV -0.5ml, p=0.01; LCI 0.02, p=0.03; time to peak expiratory flow over total expiratory time ratio: tPTEF/tE -0.01, p=0.03) or associated with wheeze (LCI 0.06, p=0.04; tPTEF/tE -0.07, p=0.002). Conclusion: LRTI in infancy has a sustained impact on lung function at 2 years, especially if recurrent or associated with wheeze. Funding: The Wellcome Trust (204755/Z/16/Z) Bill and Melinda Gates Foundation (1017641)