Associations of Early Life Ambient PM2.5 Exposure With Asthma Risk in a Cohort of Preterm Infants With Bronchopulmonary Dysplasia.

OBJECTIVE: To examine whether exposure to fine particulate matter (PM2.5) during the first year after neonatal intensive care unit (NICU) discharge is associated with asthma by age 5 among infants with bronchopulmonary dysplasia (BPD). METHODS: We conducted a retrospective cohort study of 337 infants with BPD, born between 2010 and 2019, who survived to discharge with clinical follow-up in the Children's Hospital of Philadelphia Care Network through age 5. Daily residential census block group PM2.5 exposures were estimated using a spatiotemporal machine-learning model and averaged over the first year after NICU discharge. Modified Poisson regression models with robust standard errors quantified associations of PM2.5 with asthma by age 5, adjusting for neonatal clinical factors, insurance, neighborhood deprivation, and race/ethnicity. RESULTS: By age 5 years, 169 (50.1%) infants had an asthma diagnosis. Mean annual PM2.5 exposure was 8.8 µg/m3 (SD 1.1). Each 1 µg/m3 increment of PM2.5 was associated with higher asthma risk (unadjusted RR 1.14, 95% CI: 1.03-1.25; fully adjusted aRR 1.19, 95% CI: 1.03-1.37). Compared to the lowest exposure tertile (mean 7.6 µg/m3), adjusted rates of asthma tended to be higher as exposure increased: Tertile 2 (mean 8.7 µg/m3, aRR 1.31; 95% CI: 0.98-1.74), Tertile 3 (mean 10.0 µg/m3, aRR 1.68, 95% CI: 1.17-2.4). CONCLUSIONS: Exposure to higher ambient PM2.5 in the year after NICU discharge was associated with asthma by age 5 among children with BPD. These findings highlight early-life air quality as a modifiable determinant of long-term respiratory outcomes in infants with BPD.