Reduced Lung Function at Preschool Age in Survivors of Very Low Birth Weight Preterm Infants

Background: Survivors of preterm birth are at risk of long-term respiratory consequences. The objective of this prospective study was to assess pulmonary function at preschool age of former very low birth weight (VLBW) preterm children. Methods: Lung function of children born preterm and term controls aged 5-6 years were assessed by spirometry. The results were converted to z-scores. A questionnaire regarding respiratory symptoms was completed. Associations to gestational age (GA), birth weight (BW), bronchopulmonary dysplasia (BPD), and perinatal factors were assessed. Results: In total, 85 VLBW preterm children and 29 term controls were studied. Of the preterm children, the mean GA was 28.6±2.6 weeks and the mean BW was 1047±273gm. Preterm children had significantly lower z-scores of forced expiratory volume in one second (FEV1), FEV1/forced vital capacity (FVC) ratio, and forced expiratory flow rate between 25-75% of FVC (FEF25-75), compared with term controls (-0.73 vs 0.04, p=0.002; -0.22 vs 0.39, p=0.003; -0.93 vs 0.0, p<0.001; respectively). Further segregation of the preterm group revealed significantly impaired FEV1, FEF25-75 in children at earlier gestation (≤ 28 weeks, n=45), lighter at birth (≤ 1000g, n=38), or with BPD (n=55) compared with term controls (p<0.05). There were significant negative relationships between the severity of BPD with FEV1, FVC, and FEF25-75 (p<0.05). However, no correlation between lung function measurements and respiratory symptoms was found. Conclusions: VLBW preterm infants have reduced lung function at preschool age, especially among those with younger GA, lower BW, and BPD. Additional long-term follow-up of respiratory outcomes are needed for this vulnerable population.