Geographical Differences and Temporal Improvements in Forced Expiratory Volume in 1 Second of Preterm-Born Children: A Systematic Review and Meta-analysis

IMPORTANCE: Although preterm birth is associated with later deficits in lung function, there is a paucity of information on geographical differences and whether improvements occur over time, especially after surfactant was introduced. OBJECTIVE: To determine deficits in percentage predicted forced expiratory volume in 1 second (%FEV(1)) in preterm-born study participants, including those with bronchopulmonary dysplasia (BPD) in infancy, when compared with term-born control groups. DATA SOURCES: Eight databases searched up to December 2021. STUDY SELECTION: Studies reporting spirometry for preterm-born participants with or without a term-born control group were identified. DATA EXTRACTION AND SYNTHESIS: Data were extracted and quality assessed by 1 reviewer and checked by another. Data were pooled using random-effects models and analyzed using Review Manager and the R metafor package. MAIN OUTCOMES AND MEASURES: Deficits in %FEV(1) between preterm-born and term groups. Associations between deficits in %FEV(1) and year of birth, age, introduction of surfactant therapy, and geographical region of birth and residence were also assessed. RESULTS: From 16 856 titles, 685 full articles were screened: 86 with and without term-born control groups were included. Fifty studies with term controls were combined with the 36 studies from our previous systematic review, including 7094 preterm-born and 17 700 term-born participants. Of these studies, 45 included preterm-born children without BPD, 29 reported on BPD28 (supplemental oxygen dependency at 28 days), 26 reported on BPD36 (supplemental oxygen dependency at 36 weeks’ postmenstrual age), and 86 included preterm-born participants. Compared with the term-born group, the group of all preterm-born participants (all preterm) had deficits of %FEV(1) of −9.2%; those without BPD had deficits of −5.8%, and those with BPD had deficits of approximately −16% regardless of whether they had BPD28 or BPD36. As year of birth increased, there was a statistically significant narrowing of the difference in mean %FEV(1) between the preterm- and term-born groups for the all preterm group and the 3 BPD groups but not for the preterm-born group without BPD. For the all BPD group, when compared with Scandinavia, North America and western Europe had deficits of −5.5% (95% CI, −10.7 to −0.3; P = .04) and −4.1% (95% CI, −8.8 to 0.5; P = .08), respectively. CONCLUSIONS AND RELEVANCE: Values for the measure %FEV(1) were reduced in preterm-born survivors. There were improvements in %FEV(1) over recent years, but geographical region had an association with later %FEV(1) for the BPD groups.