Exploring the Association of Male Sex With Adverse Outcomes in Severe Bronchopulmonary Dysplasia: A Retrospective, Multicenter Cohort Study

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a significant contributor to morbidity and death in infants who are born premature. Male sex is an independent risk factor for the development of BPD. However, whether male sex is associated with adverse outcomes that occur after formal diagnosis of severe BPD prior to hospital discharge remains unclear.

RESEARCH QUESTION

Is male sex associated with a higher risk of adverse outcomes in infants with established severe BPD?

STUDY DESIGN AND METHODS

A retrospective, multicenter cohort study of infants enrolled in the BPD Collaborative Registry from January 1, 2015, to June 29, 2022, was performed. Demographics, clinical characteristics, and outcomes were stratified by sex (ie, male vs female). Regression modeling was used to estimate the association of sex with the primary composite outcome of death or tracheostomy at hospital discharge.

RESULTS

We identified 1,156 infants with severe BPD, defined at 36 weeks postmenstrual age by the National Institutes of Health 2001 consensus definition. The cohort was predominantly male (59% male infants, 41% female infants). However, rates of mechanical ventilation at 36 weeks postmenstrual age (ie, type 2 severe BPD) did not differ by sex. Overall mortality rates within the cohort were low (male infants, 5.3%; female infants, 3.6%). The OR of death or tracheostomy for male-to-female infants was 1.0 (95% CI, 0.7-1.5).

INTERPRETATION

Our results lead us to speculate that, although sex is an important variable that contributes to the development and pathogenesis of severe BPD, it does not appear to be associated with adverse outcomes in this cohort of infants with established disease. The surprising results raise important questions surrounding the temporal role of biological sex in the development of severe BPD and its progression during the neonatal ICU stay. As we explore the phenotypes and endotypes of BPD, it is imperative to consider how sex modulates the disease from birth through hospital discharge.

Differences in Comorbidities and Clinical Burden of Severe Bronchopulmonary Dysplasia Based on Disease Severity

Background: The present study compared baseline characteristics, comorbidities and clinical burden of pre-term infants with type 1 and 2 severe bronchopulmonary dysplasia (BPD) Collaborative classification. Methods: This study was a prospective cohort study of pre-term (<32 weeks) very-low-birth-weight infants. Severe BPD was divided into type 1 severe BPD requiring of ≥30% oxygen and/or non-invasive ventilation at 36 weeks post-menstrual age (PMA), and type 2 severe BPD requiring invasive mechanical ventilation at 36 weeks PMA. Baseline characteristics, comorbidities, and clinical burden were compared between these two types of severe BPD. Results: Of the 1,328 infants included, 983 (74.0%) developed type 1 severe BPD, and 345 (26.0%) developed type 2 severe BPD. Lower birth weight, small for gestational age, lesser maternal pre-mature rupture of membrane, lower 5-min Apgar score, air leak, pulmonary hemorrhage, surgical ligation of patent ductus arteriosus, necrotizing enterocolitis, and late-onset sepsis were significantly associated with type 2 severe BPD. Compared with infants with type 1 severe BPD, infants with type 2 severe BPD had an increased risk of mortality (aOR 18.64, 95% CI 10.81-32.13), pulmonary hypertension (aOR 2.16, 95% CI 1.59-2.93), and tracheostomy (aOR 10.38, 95% CI 2.05-52.49). Conclusions: Our data highlight the substantially greater mortality and clinical burden in infants with type 2 severe BPD than infants with type 1 severe BPD. A comprehensive and multidisciplinary approach is needed for infants with type 2 severe BPD.