Neonatal bronchopulmonary dysplasia severity and respiratory outcomes at 3 years of age: a prospective cohort study

To examine whether bronchopulmonary dysplasia (BPD) severity is associated with pulmonary function abnormalities and asthma diagnosis risk at 3 years of age, and to support risk-stratified respiratory follow-up in children with BPD.

This prospective cohort study included 68 preterm infants admitted to the neonatal intensive care unit of The First People's Hospital of Yongkang between January 2022 and December 2022. In the study protocol, BPD was operationally defined at 36 weeks' postmenstrual age as persistent supplemental oxygen requirement [fraction of inspired oxygen (FiO2) > 0.21] to maintain target oxygen saturation of 90%-95%, together with persistent pulmonary parenchymal abnormalities on chest imaging. Severity was then categorized using a prespecified support- and oxygen-based clinical scheme informed by, but not identical to, the 2018 National Institute of Child Health and Human Development (NICHD) workshop framework. Participants were followed until 3 years of age, when conventional spirometry and guideline-based clinical asthma assessment were performed. The associations of modified BPD grade with pulmonary function indices, asthma diagnosis, and asthma clinical risk categories were analyzed.

Among the 68 infants with BPD, 29 (42.6%) had grade I BPD, 23 (33.8%) had grade II BPD, and 16 (23.5%) had grade III BPD. Sixty children completed both pulmonary function testing and asthma assessment at 3 years of age, yielding a follow-up rate of 88.2%. Percent predicted forced expiratory volume in 1 s (FEV1), FEV1/forced vital capacity (FVC), and maximal mid-expiratory flow (MMEF) were significantly lower in the grade III BPD group than in the grade I and grade II groups (all P < 0.01). The asthma diagnosis rate was significantly higher in the grade III group (46.7%) than in the grade I (8.0%) and grade II (20.0%) groups (chi-square = 8.156, P = 0.017). In an exploratory multivariable logistic regression model, grade III BPD [odds ratio [OR], 5.72; 95% confidence interval [CI], 1.89-17.31; P = 0.002] and birth weight <1,000 g (OR, 3.46; 95% CI, 1.12-10.68; P = 0.031) were associated with asthma diagnosis at 3 years of age.

Neonatal BPD severity was associated with the degree of pulmonary function impairment and with asthma diagnosis risk at 3 years of age. Children with grade III BPD had poorer long-term respiratory outcomes and should be considered a higher-risk group requiring structured longitudinal respiratory follow-up. Because this was a selected survivor cohort with structured follow-up, and because asthma diagnosis in preschool children with BPD can overlap with post-prematurity airway disease, these findings should be interpreted as risk-marker associations rather than causal evidence.