Abstract
Objective:
To assess the clinical utility and predictive ability of three commonly used definitions of bronchopulmonary dysplasia (BPD) (2001 NHLBI, 2018 NICHD, 2019 NRN) in forecasting lung function outcomes in children with a history of prematurity and BPD.
Study Design:
A retrospective chart review of 138 children with a history of prematurity and BPD who were recruited from two outpatient clinics at large tertiary medical centers was performed. Each subject’s lung disease was classified based on the three definitions of BPD. Regression analyses were performed to assess the association between lung function (FEV1 %predicted, FVC %predicted) and BPD status, defined dichotomously and by severity. Additional analyses compared lung function outcomes by need for supplemental oxygen at hospital discharge and history of pulmonary hypertension.
Results:
None of the three definitions evaluated met the criteria for an ideal definition that can both identify individuals at risk for long-term pulmonary impairment and stratify disease severity in a clinically meaningful way. In dichotomized analysis (BPD versus no BPD), both the 2018 NICHD and 2019 NRN definitions identified preterm-born individuals with significantly lower lung function parameters compared to preterm-born individuals without BPD whereas the 2001 NHLBI definition failed to distinguish between affected and unaffected individuals. A clear gradient of worsening lung function with increasing BPD severity was appreciated using the 2001 NHLBI criteria, highlighting an aspect of the definition’s relative strength in stratifying long-term risk.
Conclusions:
Newer definitions of BPD (2018 NICHD, 2019 NRN) more effectively identify children at risk for impaired pulmonary function than the older NHLBI definition. The association of supplemental oxygen requirement and diagnosis of pulmonary hypertension with lung function parameters suggests that there may be clinical indicators that are more predictive of long-term respiratory outcomes than the currently available definitions. There continues to be a need for significant refinement in the definition of BPD to improve its predictive value and guide long-term management strategies.
INTRODUCTION
Bronchopulmonary dysplasia (BPD), the major respiratory complication of preterm birth, was first described by Northway et al. in 1967[1]. Since then, significant advances in neonatal care and technology have led to an improved understanding of the pathophysiology of preterm lung disease. Consequently, our understanding of BPD has evolved from predominantly a disease of parenchymal fibrosis and airway damage to a clinical entity characterized by the arrest of alveolar development. Historically, BPD has had a treatment-based definition, so as available treatment modalities have improved, there have been several refinements in the definition of BPD. The lack of uniform diagnostic criteria has resulted in a wide variation in the reported incidence of BPD among different institutions. Furthermore, non-uniformity of BPD definitions has made it difficult to examine short- and long-term outcomes and determine the benefits of treatment modalities for these patients and their families.
Currently, there are primarily three definitions used to characterize infants and children with a history of prematurity and BPD. The National Institutes of Health (NIH) consensus definition, proposed in 2001, outlined differing criteria for infants who were born at less than 32 weeks gestation and those born at greater than 32 weeks gestation[2]. For those born at less than 32 weeks gestation, BPD was defined as “infants who require supplemental oxygen for at least 28 days and at 36 weeks postmenstrual age (PMA).” This definition added categories of mild (breathing room air), moderate (need for <30% oxygen), and severe (need for ≥ 30% oxygen and/or positive pressure), depending on supplemental oxygen and positive-pressure requirements at 36 weeks post-menstrual age (PMA) or discharge, whichever comes first. While studies have shown some association between this definition of BPD and long-term neurodevelopmental outcomes[3], one of the primary disadvantages of this definition is that it attempts to classify a chronic disease based on oxygen exposure at a singular point in time. Additionally, it does not account for other factors that can influence oxygen saturation, including altitude, airway malacia, apnea of prematurity, and use of certain medications (diuretics, steroids, pulmonary vasodilators).
In 2018, the National Institute of Child Health and Development (NICHD) published recommendations for a revised definition of BPD[4] that again primarily considered respiratory support, including increased FiO2, at 36 weeks’ PMA but also required radiographic evidence of parenchymal lung disease for diagnosis. Additionally, this proposed definition included three grades of severity as well as a separate grade for those infants who suffer an early death from persistent parenchymal lung disease and respiratory failure.
The most recent criteria proposed by Jensen et al.[5], published in 2019 and based on data from the Neonatal Research Network (NRN), characterized BPD severity exclusively based on the level of respiratory support at 36 weeks’ PMA, irrespective of oxygen requirement at the time of assessment. These criteria were based on an evidence-based approach to predict respiratory and neurodevelopmental outcomes at 18-26 months corrected age; however, their efficacy in predicting long-term outcomes requires further evaluation.
While several studies have attempted to validate the different definitions of BPD that are currently available and in use using short-term outcomes[6, 7], few studies have attempted to determine whether the various definitions of BPD available can accurately predict patients at the highest risk of long-term respiratory morbidity in the outpatient setting. Spirometry provides an objective, quantitative, and standardized measure of pulmonary function and is a critical tool for the longitudinal assessment of respiratory status. As adults and children with a history of prematurity and BPD are at increased risk of chronic airflow limitation and impaired pulmonary growth[8, 9], spirometry offers critical insight into the enduring impact of early lung injury. Therefore, the goal of this study was to assess the clinical applicability of the 2001 NHLBI, 2018 NICHD, and 2019 NRN definitions and their predictive ability for subsequent lung function testing in a population of children with a history of prematurity and BPD.
METHODS
Study Population:
A retrospective chart review was performed using patients (n=138) recruited from outpatient BPD clinics at two academic medical centers (Johns Hopkins Children’s Center, Children’s Hospital of Philadelphia) between January 2008 and December 2024, were at least 5 years of age as of 1/1/2025, and had adequately performed spirometry between the ages of five and seven years. All subjects were born at less than or equal to 36 weeks gestation and presented with respiratory symptoms. While at the time of enrollment in the study, subjects were outpatients at a pulmonary clinic at one of two medical centers, they received their neonatal care at a variety of neonatal intensive care units (NICUs) across several states prior to referral to the outpatient BPD clinic for follow-up. Both tertiary care centers obtained approval from local institutional review boards (JHH: NA_00051884, CHOP: 20-017614), and informed consent was obtained from caregivers.
Data Collection:
Clinical Data:
Clinical data were obtained through chart review for birth parameters, clinical characteristics, and pulmonary function testing data obtained in early childhood. Each subject’s BPD severity was assessed based on the three aforementioned definitions including the 2001 National Heart, Lung, and Blood Institute (NHLBI) consensus definition, the 2018 National Institute of Child Health and Human Development (NICHD) definition, and the NRN-based definition proposed by Jensen et al. in 2019. Pulmonary hypertension was defined as being present if observed by a clinically obtained echocardiogram on or after 36 weeks corrected gestational age.
Pulmonary Function Testing:
Patients performed spirometry between five and seven years of age at a routine clinic visit when well and without symptoms of an acute respiratory tract infection. Testing was performed using MedGraphics Platinum Elite Series Plethysmograph and interpreted according to American Thoracic Society (ATS) and European Respiratory Society (ERS) standards. Patients were adequately instructed and trained before proceeding with testing. Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were recorded and adjusted for sex, age, and height using Global Lung Function Initiative (GLI) race-neutral equations[10]. Spirometry measurements were accepted if they met the acceptability and repeatability criteria of ATS and ERS. All spirometry performed and used in the analysis was interpreted by a board-certified pediatric pulmonologist.
Statistical Methods:
Descriptive statistics were used to describe the demographic and clinical characteristics of the study population. Linear regression analysis was performed employing FEV1 %predicted and FVC %predicted as dependent variables and dichotomized variable for BPD (any BPD versus no BPD) using each of the three definitions (2001 NHLBI, 2018 NICHD, and 2019 NRN) as independent variables. Regression analysis was repeated using graded definition of BPD (mild, moderate, and severe and removing those subjects who did not meet criteria for a diagnosis of BPD based on the definition used) as independent variables. A one-way analysis of variance (ANOVA) was conducted to determine whether there were differences between the different BPD severity groups (mild, moderate, severe) means on FEV1% predicted and FVC %predicted. When differences were observed (p < 0.05), post hoc comparisons were conducted using the Bonferroni correction to adjust for multiple testing across the three levels of BPD severity. This correction was applied to control the family-wise error rate, given the repeated comparisons of the same outcome across different classification criteria. Finally, lung function parameters (FEV1 %predicted and FVC %predicted) were compared between infants discharged home on supplemental oxygen and those discharged home in room air and then again between those with pulmonary hypertension and those without pulmonary hypertension using independent sample t-tests. STATA IC 18 (StataCorp LP) was used for analyses. p Values less than 0.05 were considered statistically significant.
RESULTS
Demographics and Clinical Characteristics
A total of 138 subjects, 88 (63.8%) from the Johns Hopkins (JHH) BPD registry and 50 (36.2%) from the Children’s Hospital of Philadelphia (CHOP) BPD registry, met the inclusion criteria and were included in the analysis. The demographic and clinical characteristics of the study population are summarized in Table 1. Notably, the study population was 49.3% female and had an average gestational age of 26.9 ± 2.9 weeks. A total of 54.6% of subjects identified as nonwhite race/ethnicity. The mean median household income for the study population was $62,800 ± $20,000, and 59.4% had public insurance (median household income in the U.S.: $62,843; Maryland: $84,805; Pennsylvania: $61,744). A total of 55 patients (39.9%) required supplemental oxygen at the time of discharge from the NICU with an average amount of 0.33 ± 0.29 liters per minute. 28.3% of the population had a gastrostomy (GT) placed, 19.6% underwent Nissen fundoplication, and 20.3% were diagnosed with pulmonary hypertension. In terms of lung function parameters, the mean FEV1 %predicted among the entire study population was 79.0% ± 18.4%, and the mean FVC %predicted was 85.6% ± 21.3%. There was no significant difference in FEV1 % predicted or FVC % predicted between the two different clinical sites (JHH and CHOP).
Table 1.
Study Population Demographics
| Mean ± S.D. [Range] | Study Population (n = 138) | |||
|---|---|---|---|---|
| Demographic Characteristics | Sex (% female) | 49.3% | ||
| Gestational age (weeks) | 26.9 ± 2.9 [22.7, 35.5] | |||
| Birth weight (grams, n=136) | 1002 ± 506 [380, 3150] | |||
| Birth weight percentile (%, n=136) | 43.2 ± 25.6 [3, 99] | |||
| Race/ethnicity (% non-white; n=130) | 54.6% | |||
| Median household income ($’000s) | 62.8 ± 20.0 [22.0, 108.1] | |||
| Public insurance (% yes) | 59.4% | |||
| Clinical Characteristics | Supplemental oxygen at NICU discharge (% yes) | 39.9% | ||
| Oxygen amount at NICU discharge (LPM; n = 55) | 0.33 ± 0.29 [0.06, 1.5] | |||
| Gastrostomy tube (% yes) | 28.3% | |||
| Nissen fundoplication (% yes) | 19.6% | |||
| Pulmonary hypertension (% yes) | 20.3% | |||
| Severity of BPD | 2001 NHLBI Consensus Definition (n=119) | None | 7.6% | |
| Mild | 12.6% | |||
| Moderate | 35.3% | |||
| Severe | 44.5% | |||
| 2018 NICHD Definition (n=85) | None | 41.1% | ||
| Mild | 30.6% | |||
| Moderate | 7.1% | |||
| Severe | 21.2% | |||
| 2019 Jensen Criteria (n=118) | None | 21.2% | ||
| Mild | 33.1% | |||
| Moderate | 32.2% | |||
| Severe | 13.6% | |||
| Lung Function | Forced Expiratory Volume in 1 second (FEV1 % predicted) | 79.0 ± 19.5 [33, 126] | ||
| Forced Expiratory Volume in 1 second (FEV1 % predicted) – Site 1 (JHH) | 77.6 ± 18.4 [34, 122] | |||
| Forced Expiratory Volume in 1 second (FEV1 % predicted) – Site 2 (CHOP) | 81.6 ± 21.4 [33, 126] | |||
| Forced Vital Capacity (FVC % predicted) | 85.6 ± 21.3 [35, 182] | |||
| Forced Vital Capacity (FVC % predicted) – Site 1 (JHH) | 85.9 ± 21.5 [45, 182] | |||
| Forced Vital Capacity (FVC % predicted) – Site 2 (CHOP) | 84.9 ± 21.3 [35, 139] | |||
BPD Definitions
Of the 138 subjects, 119 (86.2%) children had data available that allowed them to be classified according to the severity of their BPD per the 2001 NHLBI consensus definition with 9 (7.6%) children with confirmed chronic lung disease of prematurity (did not meet the 2001 NHLBI guidelines for BPD but were born prematurely and have ongoing respiratory symptoms), 15 (12.6%) children with mild BPD, 42 (35.3%) with moderate BPD, and 53 (44.5%) with severe BPD. The remaining 19 (13.8%) children lacked detailed clinical data to allow classification based on respiratory support at 36 weeks corrected gestational age. Using the 2018 NICHD definition of BPD, 85 (61.6%) of the 138 subjects had data available that allowed them to be classified according to the severity of their BPD. 35 (41.1%) had chronic lung disease of prematurity (did not meet NICHD criteria for BPD), 26 (30.6%) had mild BPD, 6 (7.1%) had moderate BPD, and 18 (21.2%) had severe BPD. A total of 118 (85.5%) subjects had data available that allowed the severity of their BPD to be classified according to the 2019 NRN definition. 25 (21.2%) children did not meet criteria for BPD, 39 (33.1%) of children had mild BPD, 38 (32.2%) children had moderate BPD, and 16 (13.6%) children had severe BPD.
Lung Function Parameters
Lung function parameters (FEV1 % predicted and FVC %predicted) differed by BPD status (BPD versus no BPD) depending on the diagnostic definition used (Table 2). Using the 2001 NHLBI definition, there was no statistically significant difference in either FEV1 %predicted (80.4% ± 21.1 versus 78.9% ± 19.5, p=0.798) or FVC %predicted (93.6% ± 31.3 versus 84.8% ± 20.1, p=0.17) between children with BPD of any severity and children without BPD. In contrast, both the 2018 NICHD and 2019 NRN definitions identified significantly impaired lung function among individuals with BPD. Using the NICHD criteria, FEV1 %predicted and FVC %predicted were significantly lower in those with BPD of any severity (75.7% ± 19.0 and 81.5% ± 19.7) compared to those without BPD (85.8% ± 19.1 and 93.8% ± 19.1 22.3; p=0.004 and p=0.0012, respectively). Similarly, using the NRN definition, subjects with BPD of any severity had lower FEV1 %predicted (76.6% ± 18.9 versus 88.1% ± 19.6, p=0.004) and FVC %predicted (82.4% ± 19.2 versus 97.4% ± 24.9, p=0.0006) compared to those without BPD.
Table 2.
Lung Function Parameters by BPD Definition Comparing Subjects with BPD (mild, moderate, or severe) to Subjects without BPD
| Forced Expiratory Volume in 1 second (FEV1 % predicted) Mean ± S.D. |
No diagnosis of BPD | BPD (mild, moderate, severe) | P value |
|---|---|---|---|
| 2001 National Heart, Lung, and Blood Institute (NHLBI) consensus definition | 80.4 ± 21.1 (n=12) | 78.9 ± 19.5 (n=126) | 0.798 |
| 2018 National Institute of Child Health and Human Development (NICHD) definition | 85.77 ± 19.1 (n=46) | 75.7 ± 19.0 (n=92) | 0.004 |
| 2019 Jensen definition | 88.1 ± 19.6 (n=29) | 76.6 ± 18.9 (n=109) | 0.004 |
|
Forced Vital Capacity
(FVC % predicted) Mean ± S.D. |
No diagnosis of BPD | BPD (mild, moderate, severe) | P value |
| 2001 National Heart, Lung, and Blood Institute (NHLBI) consensus definition | 93.6 ± 31.3 (n=12) | 84.8 ± 20.1 (n=126) | 0.17 |
| 2018 National Institute of Child Health and Human Development (NICHD) definition | 93.8 ± 22.3 (n=46) | 81.5 ± 19.7 (n=92) | 0.0012 |
| 2019 Jensen definition | 97.4 ± 24.9 (n=29) | 82.4 ± 19.2 (n=109) | 0.0006 |
After removing subjects with chronic lung disease who did not meet the criteria for BPD, when stratified by BPD severity (Table 3), lung function declined progressively with increasing severity under the 2001 NHLBI definition. FEV1 and FVC %predicted values were highest in those with mild BPD (94.1 ± 18.0 and 99.4 ± 19.4, respectively), and significantly lower in moderate (79.5 ± 16.6 and 83.9 ± 18.5) and severe BPD groups (72.6 ± 19.9 and 80.7 ± 20.6; P = 0.0005 for FEV1, P = 0.0062 for FVC). Post hoc analysis confirmed significant differences between mild and both moderate and severe groups, but not between those with moderate and those with severe disease. In contrast, the NICHD and NRN definitions did not demonstrate statistically significant trends in FEV1 or FVC % predicted across severity levels, though numerically lower values were observed in more severe groups. For the NRN definition, FEV1 % predicted decreased from 79.6 ± 17.5 in mild BPD to 66.2 ± 17.5 in severe BPD (P = 0.06), suggesting a potential but non-significant gradient in lung function decline.
Table 3.
Lung Function Parameters by BPD Definition and Severity
| Lung Function Parameters | |||||
|---|---|---|---|---|---|
| Forced Expiratory Volume in 1 second (FEV1 % predicted) Mean ± S.D. |
P-value | Forced Vital Capacity (FVC % predicted) Mean ± S.D. |
P-value | ||
| 2001 National Heart, Lung, and Blood Institute (NHLBI) consensus definition (n=110) | Mild (n=15) | 94.1 ± 18.0 | 0.00051 | 99.4 ± 19.4 | 0.0062 2 |
| Moderate (n=42) | 79.5 ± 16.6 | 83.9 ± 18.5 | |||
| Severe (n=53) | 72.6 ± 19.9 | 80.7 ± 20.6 | |||
| 2018 National Institute of Child Health and Human Development (NICHD) definition (n=50) | Mild (n=26) | 78.1 ± 19.1 | 0.22 | 81.8 ± 21.2 | 0.84 |
| Moderate (n=6) | 63.5 ± 27.3 | 78.5 ± 31.4 | |||
| Severe (n=18) | 71.8 ± 17.0 | 78.2 ± 17.4 | |||
| 2019 Jensen definition (n=93) | Mild (n=39) | 79.6 ± 17.5 | 0.06 | 83.8 ± 19.3 | 0.23 |
| Moderate (n=38) | 75.9 ± 20.0 | 83.6 ± 20.4 | |||
| Severe (n=16) | 66.2 ± 17.5 | 74.4 ± 18.4 | |||
ANOVA with Bonferroni correction demonstrates a significant difference in FEV1 between groups (p=0.0005) and specifically, a significant difference between those with mild disease and those with moderate disease (p=0.029) and those with mild disease and those with severe disease (p=0.000). However, there is no significant difference between those with moderate disease and those with severe disease (p=0.220).
ANOVA with Bonferroni correction demonstrates a significant difference in FVC between groups (p=0.0062) and specifically, a significant difference between those with mild disease and those with moderate disease (p=0.031) and those with mild disease and those with severe disease (p=0.005). However, there is no significant difference between those with moderate disease and those with severe disease (p=1.0).
To further explore clinical predictors of long-term pulmonary outcomes not directly included in any of the three definitions of BPD, lung function was compared based on the need for supplemental oxygen at hospital discharge (Table 4) and a diagnosis of pulmonary hypertension (Table 5) at 36 weeks’ corrected gestational age. Children discharged home on supplemental oxygen had a lower mean FEV1 % predicted (75.8% ± 20.40) and FVC (81.1% ± 19.9) compared to those discharged in room air (FEV1: 81.1% ± 18.7; FVC: 88.5% ± 21.9). Although the difference in FEV1 did not reach statistical significance (p=0.12), the reduction in FVC approached significance (p=0.05). Similarly, lung function parameters were noted to be significantly impaired in children with a diagnosis of pulmonary hypertension as compared to those without pulmonary hypertension with a lower mean FEV1 (70.7% ±. 19.1 versus 81.1% ± 19.1; p=0.01) and FVC (75.8% ± 19.2 versus 88.1% ± 21.2; p=0.006). These findings suggest that there may be some clinical indicators that are more predictive of long-term respiratory outcomes than the currently available definitions of BPD.
Table 4.
Lung Function Parameters by Supplemental Oxygen Requirement at Discharge
| Discharged home on supplemental oxygen | Discharged home in room air | P value | |
|---|---|---|---|
|
Forced Expiratory Volume in 1 second (FEV1 % predicted) Mean ± S.D. |
75.8 ± 20.4 (n=55) | 81.1 ± 18.7 (n=83) | 0.12 |
|
Forced Vital Capacity (FVC % predicted) Mean ± S.D. |
81.1 ± 19.9 (n=55) | 88.5 ± 21.9 (n=83) | 0.05 |
Table 5.
Lung Function Parameters by Diagnosis of Pulmonary Hypertension
| Diagnosed with pulmonary hypertension | No pulmonary hypertension | P value | |
|---|---|---|---|
|
Forced Expiratory Volume in 1 second (FEV1 % predicted) Mean ± S.D. |
70.7 ± 19.1 (n=28) | 81.1 ± 19.1 (n=110) | 0.01 |
|
Forced Vital Capacity (FVC % predicted) Mean ± S.D. |
75.8 ± 19.2 (n=28) | 88.1 ± 21.2 (n=110) | 0.006 |
Sensitivity Analysis
To evaluate the potential influence of socioeconomic status (SES), which is known to affect long-term pulmonary outcomes through access to care and exposure to known environmental risk factors such as air pollution and tobacco smoking, on lung function outcomes, a sensitivity analysis was performed using insurance status. Subjects with public insurance had a mean FEV1% predicted that was 5 percentage points lower than individuals with private insurance (76.8% ± 17.3 versus 82.2% ± 22.2; p=0.11); however, this difference was not significant. Similarly, individuals with public insurance had a mean FVC % predicted that was 5 percentage points lower than those with private insurance, but this difference was not significant (83.2% ± 17.9 versus 89.0% ± 25.3; p=0.11).
DISCUSSION
While previous studies have attempted to evaluate the definitions of BPD based on patient classification and short-term outcomes[11], to our knowledge, this is one of the first studies to assess the association between the three most commonly used definitions of BPD and early childhood spirometry in a cohort of preterm-born children. Of the three definitions evaluated, none meet the criteria for an ideal definition that is able to identify individuals at risk for long-term pulmonary impairment and stratify disease severity in a clinically meaningful way.
We found that both the 2018 NICHD and 2019 NRN definitions identified preterm-born individuals with significantly lower forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) compared to preterm-born individuals without BPD. The 2001 NHLBI definition failed to distinguish between affected and unaffected individuals, suggesting that more contemporary classification systems, which incorporate some of the newer modalities of respiratory support currently used in the NICU, may better capture individuals at risk for long-term pulmonary impairment[12]. These findings echo those from a recent study of 100 infants with severe BPD, which demonstrated that more recent definitions, in this case the NRN definition and a definition proposed by the International BPD Collaborative, were better able to predict the severity of BPD and the need for long-term invasive ventilatory support[11].
Importantly, we observed a clear gradient of worsening lung function with increasing BPD severity when using the 2001 NHLBI criteria. Children classified as having moderate or severe BPD had significantly lower FEV1 and FVC values compared to those with mild disease, with no significant difference between moderate and severe groups. Although similar trends were observed using the NICHD and NRN definitions, these did not reach statistical significance, which may be due to smaller subgroup sizes and differences in how these definitions classify disease severity. Ultimately, these findings underscore the challenge of harmonizing BPD classification schemes and highlight the NHLBI definition’s relative strength in stratifying long-term risk.
Our results also suggest that clinical indicators of disease severity at discharge, such as the need for home supplemental oxygen, may be a stronger predictor of poorer long-term pulmonary function. This aligns with previous studies suggesting that oxygen dependency at discharge is a marker of underlying lung pathology and may be a predictor of ongoing respiratory morbidity[13, 14]. The presence of pulmonary hypertension was strongly associated with a significantly reduced FEV1 and FVC. This reinforces prior evidence that pulmonary vascular disease contributes to or coexists with impaired alveolar development, likely contributing to compromised pulmonary function in this population. Identifying and managing pulmonary hypertension in infancy may therefore have implications not only for short-term outcomes, as pulmonary hypertension has been shown to increase morbidity and mortality in this population [15, 16], but also for long-term respiratory health.
There are several limitations that merit consideration, including the study’s retrospective design, which may introduce selection bias and limit causal inference. Second, sample sizes for some subgroups – particularly those defined by newer BPD classification systems – were modest, reducing the power to detect statistically significant differences in certain comparisons. Our study population was limited to children able to reliably perform spirometry, thereby excluding those with neurocognitive impairment or artificial airways. Future research incorporating alternative lung function measures – such as oscillometry – could enable inclusion of these patients. In addition, there are several early-life factors that may influence lung function, such as allergic sensitization, passive smoke exposure, significant lower respiratory tract infections, and indoor and outdoor air pollution, were not captured between BPD diagnosis and early childhood lung function testing. Insurance status was used as a proxy for socioeconomic status; however, it may not fully capture all dimensions of socioeconomic risk that could influence long-term pulmonary outcomes[17]. Finally, spirometric data were collected at a single time point, precluding assessment of longitudinal trends, which should be evaluated in future studies.
In summary, our findings suggest that contemporary BPD definitions, particularly those from NICHD and NRN, more effectively identify children at risk for impaired pulmonary function than the older NHLBI definition; however, there continues to be a need for significant refinement in the definition of BPD to improve its predictive value and guide long-term management strategies for this vulnerable population.
Funding/Support:
This work was supported by R03HD109442 (JMC, SAM) and R01HL169859 (JMC, SAM). The funding sources had no involvement in the writing of the manuscript or the decision to submit.
Footnotes
Conflicts of Interest:
The authors declare no conflicts of interest .
Data Availability Statement:
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.