Lung function in young adulthood in relation to moderate-to-late preterm birth.

Background: Moderate-to-late preterm birth (32 to <37 weeks of gestation) has been associated with impaired lung function in adolescence, but data in adulthood and physiological phenotyping beyond spirometry are scarce. We aimed to investigate lung function development from adolescence into young adulthood and to provide physiological phenotyping in individuals born moderate-to-late preterm.

Methods: Lung function data from individuals born moderate-to-late preterm (n=110) and term (37 to <42 weeks of gestation, n=1895) in the Swedish birth cohort BAMSE were used for analysis and included dynamic spirometry, fractional exhaled nitric oxide and multiple breath nitrogen wash-out. Data from 16- and 24-year follow-ups were analysed using regression models stratified on sex and adjusted for smoking. Data-driven latent class analysis was used to phenotype moderate-to-late preterm individuals at 24 years, and groups were related to background factors.

Results: Males born moderate-to-late preterm had lower forced expiratory volume in 1 s (FEV₁) at 24 years of age (-0.28 z-score, p=0.045), compared to males born term. In females, no difference was seen at 24 years, partly explained by a significant catch up in FEV₁ between 16 and 24 years (0.18 z-score, p=0.01). Lung function phenotypes described as "asthma-like", "dysanapsis-like" and "preterm reference" were identified within the preterm group. Maternal overweight in early pregnancy was associated with "asthma-like" group membership (OR 3.59, p=0.02).

Conclusion: Our results show impaired FEV₁ at peak lung function in males born moderate-to-late preterm, while females born moderate-to-late preterm had significant catch up between the ages of 16 and 24 years. Several phenotypes of lung function impairment exist in individuals born moderate-to-late preterm.