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.