Physical fitness trajectories from childhood to adolescence in extremely preterm children: A longitudinal cohort study

ObjectiveCohort studies on physical fitness (PF) in former extremely preterm children are scarce and yield conflicting results. Therefore, this study aimed to assess the effect of extremely preterm birth on PF in school-age with a focus on bronchopulmonary dysplasia (BPD). MethodsEighty school-aged children were enrolled in the longitudinal cohort study. Fifty were born extremely preterm (<completed 28 weeks of gestation): 19 had BPD, and 31 did not; 30 term-born healthy children were included as controls. They were monitored annually throughout primary school (ages 7-14 years) with eight annual fitness testings within the Slovenian national surveillance system of children's somatic and motor development (SLOfit). The physical fitness index (PFI), calculated as the mean of percentiles of eight fitness tests, was used as an indicator of overall PF. Generalised estimating equations were used to compare changes in PFI between ages 7 and 14 in the three cohort groups: preterm children with BPD, preterm children without BPD and term controls. ResultsPreterm children with BPD had significantly and persistently lower PFI than preterm children without BPD and term-born children throughout primary school age. Their PFI was less than half that of national median values (15.1st-19.7th percentile). Preterm children without BPD experienced progressive improvement in PFI during their school age (from 32.6th to 44.7th percentile of national median PFI values), while the ones with BPD did not. ConclusionExtreme prematurity per se is not a risk factor for lower PF at school age. However, if complicated by BPD, PF is significantly and sustainably reduced.