DISCUSSION
Our study examined the relationship between area socioeconomic deprivation and respiratory outcomes for infants with BPD using registry data. We found that infants and young children with BPD who lived in disadvantaged areas were more likely to have adverse respiratory outcomes including emergency department visits, re-hospitalizations, and activity limitations after adjusting for gestational age, race, and insurance status. These findings are consistent with prior studies that have linked deprivation with worse outcomes for a number of pediatric diseases.10-23 Compared to traditional socio-economic measures of individual income or insurance status, a potential advantage of area-level indices such as the ADI is their ability to capture community-level effects. Additionally, area-level indices provide an assessment of the joint effect of multiple risk factors, and this composite measure may be less likely to be influenced by anomalies in a single variable.30 Our study capturing multiple community-level factors assessed with the ADI illustrates that early-life community exposures are associated with poorer respiratory outcomes in preterm infants/children with BPD, likely contributing to health disparities in the very young.
A French study using a socioeconomic deprivation index linked to census data found that the respiratory-related re-hospitalization rate was almost 3-fold higher for infants living in deprived neighborhoods (adjusted incidence rate ratio: 2.79;p <0.01).26 We observed a similar effect in our population (hospital readmissions adjusted OR 1.66;p =0.030). Neighborhood deprivation has been associated with adverse outcomes in other pediatric respiratory diseases as well. A national registry study found a significant association between ADI and respiratory outcomes in pediatric cystic fibrosis, specifically finding that children residing in the most deprived tertile had 2.8% lower forced expiratory volumes, 1.2 times more IV treatment nights, and a 20% higher risk of having more than 2 pulmonary exacerbations when compared to counterparts in the least deprived tertile.19 Similarly, studies of pediatric asthma have demonstrated associations between neighborhood deprivation and increased emergency calls for asthma exacerbations,16 and hospital readmissions for asthma, although the latter association is modified by health insurance coverage.17,18 It should be noted that not all studies of pediatric asthma have identified associations between the ADI and adverse outcomes.31
The connection between area deprivation and poorer outcomes in BPD is likely multifactorial. Neighborhoods with higher ADI scores may increase a patient’s exposure to environmental risk factors for poor air quality, such as traffic pollution and tobacco smoke.32,33Lower household income has been associated with increased risk for respiratory morbidities in prior studies.24 Income may be a limiting factor preventing families from finding housing with quality air ventilation, the lack of which has been associated with respiratory disease.34 Additionally, poverty, particularly inside cities such as Baltimore and Philadelphia, may be associated with residential crowding, which increases a child’s potential exposure to respiratory diseases.35,36Neighborhood deprivation may also be linked to decreased access to healthcare, which could make early outpatient intervention more difficult, leading to higher chances of requiring emergency care or hospitalization. Further studies will be necessary to delineate the pathophysiology behind this relationship.
In terms of factors that may play a role prior to NICU discharge, we found an association between deprivation and gestational age, suggesting that living in an area with high deprivation may increase the risk of preterm birth, similar to previous studies.37,38 There may also be NICU-level factors as well; although subjects in the most deprived tertiles were born at earlier gestational ages and lower birth weights, the length of initial hospitalization did not differ between first and third tertiles, nor did the frequency of use of medical technologies. It is unclear whether the similar initial hospitalization length and use of medical technologies reflects a “level playing field” at NICU discharge for all tertiles or whether subjects in the most deprived tertile may have less support at discharge than they could require based on gestational age and birthweight.
Limitations: A potential disadvantage of area-level indices is that neighborhood averages may not reflect the socioeconomic situation of families that may be outliers in their area, therefore individual patient situations should always be considered in the clinical setting. Additionally, based on data availability, ADI scores were aggregated to ZIP codes, with inevitable loss of geographic resolution and precision of estimates, especially in areas where poor and affluent neighborhoods are in close proximity.39 Patients enrolled in this study were from Baltimore and Philadelphia metropolitan areas, and results may not be generalizable outside of these geographic regions, or to patients not residing in the catchment area of a metropolitan tertiary care center. Our study population also has more severe respiratory disease (53% met definition for severe BPD) compared to the preterm population as a whole (16% of NHLBI validation cohort met criteria for severe BPD),40 which may limit generalizability.
Conclusions: We found that area-level socioeconomic deprivation is associated with several poor respiratory outcomes in a contemporary cohort of infants and young children with BPD. Thus, assessment of area deprivation using the ADI may be a useful screening tool in an outpatient setting to identify young children with BPD at increased risk for adverse outcomes or to identify areas that would benefit from targeted public health interventions to improve respiratory health.