Statistical analysis
Continuous variables were described using medians and interquartile
ranges (IQR). Categorical variables were described using counts and
percentages. Patient characteristics and outcomes were stratified by
primary exposure and compared using Chi-square test or Fisher’s exact
test for categorical variables as appropriate and Wilcoxon rank sum test
for continuous variables. Generalized linear models were used for
comparisons in child-level count data while generalized linear mixed
models were used for comparisons in culture-level data to account for
the correlation within child clusters.
Poisson regression models with robust standard errors were used to
examine the association between each predictor group (of dichotomous
culture status) and children’s 3-year outcomes, adjusted for covariates
including sex, race, insurance type, and number of complex chronic
conditions and accounting for correlation within child clusters.
Kaplan-Meier survival analyses with log-rank test were used to assess
death-free survival. Race was included in analysis due to known racial
differences in outcomes among infants with BPD,23 and
as a proxy for structural racism and bias.
Analyses were performed with SAS V9.4 (SAS Institute Inc., Cary, NC,
USA) and with R v4.1.1 (Vienna, Austria).24P -values <0.05 were considered statistically
significant.