METHODS
Study Population: This study was conducted using a
retrospective review of a database of subjects recruited from outpatient
BPD pulmonary clinics at Johns Hopkins University (n=911) and the
Children’s Hospital of Philadelphia (n=125) between January 2008 and
October 2021. Two subjects in the Johns Hopkins University registry were
excluded as ADI scores were not available for their zip codes to yield a
study population of 1034 subjects. Inclusion criteria included
prematurity (<37 weeks gestation) and a diagnosis of BPD by
NHLBI guidelines.27 This study was approved by the
Johns Hopkins University Institutional Review Board (Protocol #:
NA_00051884; all caregivers consented) and the Children’s Hospital of
Pediatrics Institutional Review Board (IRB# 20-017614; determined to
meet exemption criteria).
Demographic and clinical data: Clinical data were obtained
through chart review. Race and ethnicity were self-reported. Birth
weight percentiles were derived from national U.S.
data.28 Home oxygen and ventilator use were defined as
use at the time of initial NICU discharge. Pulmonary hypertension was
defined by the presence of pulmonary hypertension on echocardiogram on
or after 36 weeks corrected age.29 Acute care for
respiratory issues (occurrence of ER visits, hospitalizations, need for
inhaled corticosteroids, and antibiotic use) and chronic symptom
outcomes (trouble breathing, need for rescue medications, shortness of
breath, nighttime symptoms) were collected through questionnaires at
outpatient visits between ages 0-3 years.
Area deprivation scores: The 2019 ADI, created by the
University of Wisconsin, is a validated measure of the socioeconomic
context for U.S. census block groups, proxies for
neighborhoods.9 The index (national scale from 0-100,
with higher scores indicating worse deprivation) is constructed from 17
variables in the American Community Survey 5-year estimates. ADI scores
for the study population were calculated using residential 5-digit ZIP
codes and employing the 9-digit ZIP code crosswalk built to correspond
to Census block groups. Median ADI scores were computed from all ADI
values for block groups within each 5-digit ZIP code, excluding post
office boxes, businesses, or large footprint entities, as done
previously.19
Statistical methods: Subjects were separated into tertiles by
median ADI scores for a zip code (ADI > 51.5 (n=345), ADI
32.5-51 (n=347), ADI =< 32 (n=342). Demographics and baseline
clinical data of the highest and lowest tertiles were compared using chi
square tests and t-tests. Associations between ADI tertiles and clinical
outcomes were assessed using logistic regression mixed models adjusted
for age at outcome data collection and potential demographic/clinical
confounders (subjects with missing confounding variables were excluded
from regression models); models were nested by individual and center.
Sensitivity analyses were conducted using mean ADI scores for a zip
code. All statistical analyses were conducted using Stata 17 (StataCorp;
College Station, TX). P values <0.05 were considered
statistically significant.