Early growth characteristics and the risk of reduced lung function and asthma: A meta-analysis of 25,000 children

Background Children born preterm or with a small size for gestational age are at increased risk for childhood asthma. Objective We sought to assess the hypothesis that these associations are explained by reduced airway patency. Methods We used individual participant data of 24,938 children from 24 birth cohorts to examine and meta-analyze the associations of gestational age, size for gestational age, and infant weight gain with childhood lung function and asthma (age range, 3.9-19.1 years). Second, we explored whether these lung function outcomes mediated the associations of early growth characteristics with childhood asthma. Results Children born with a younger gestational age had a lower FEV 1 , FEV 1 /forced vital capacity (FVC) ratio, and forced expiratory volume after exhaling 75% of vital capacity (FEF 75 ), whereas those born with a smaller size for gestational age at birth had a lower FEV 1 but higher FEV 1 /FVC ratio ( P 1 but lower FEV 1 /FVC ratio and FEF 75 in childhood ( P 1 , FEV 1 /FVC ratio, and FEF 75 might explain 7% (95% CI, 2% to 10%) to 45% (95% CI, 15% to 81%) of the associations between early growth characteristics and asthma. Conclusions Younger gestational age, smaller size for gestational age, and greater infant weight gain were across the full ranges associated with childhood lung function. These associations explain the risk of childhood asthma to a substantial extent.