Discussion

Our study found associations of maternal education, food stamp programme participation, and health insurance coverage type with outcomes of caregiver-related health, activity limitation, requirement of specialised medical equipment, and receipt of special education services. However, these socio-economic characteristics exhibited inconsistent associations with the outcomes in our study, and none were associated with missed days of school due to illness. Children growing up with CHD may experience reduced quality of life and greater likelihood of functional limitation related to this condition. ^{Reference Ernst, Marino and Cassedy3,Reference Xiang, Su and Liu4,Reference Eagleson, Justo, Ware, Johnson and Boyle15} Lower quality of life corresponds with increased disease severity and medical care utilisation, ^{Reference Ernst, Marino and Cassedy3} and these outcomes may be exacerbated by socio-economic disadvantage. Specific concerns for these families include access to transportation, health literacy, and ability to pay for health care. Recent studies have noted the strong impact of psychosocial factors on quality of life, including anxiety and stress, for both patients and their families. ^{Reference Ernst, Marino and Cassedy3,Reference Denniss, Sholler, Costa, Winlaw and Kasparian16} While the impact of socio-economic status has been described for the health of infants with CHD, including those who undergo cardiac surgery, ^{Reference Bucholz, Sleeper and Newburger9,Reference Lee, Cinanni and Di Cristofaro11} our study adds new data on the association of socio-economic characteristics with health and functional status outcomes in later childhood, including among children in the community who may no longer be under cardiology follow-up.

Considering specific measures of socio-economic status, we found that lower maternal educational attainment correlated with worse caregiver-rated health among children with CHD. In a previous study, low socio-economic status was adversely associated with quality of life among children with CHD, a relationship that appeared to be mediated by lower health literacy among caregivers. ^{Reference Bucholz, Sleeper and Newburger9} Similarly, we found that children with CHD who had neither public nor private insurance were especially likely to experience functional limitations, and to be receive special education services. In the general paediatric population, disruption of health insurance coverage is associated with a lack of continuity in care, resulting in unmet healthcare needs. ^{Reference Tumin, Miller, Raman, Uffman and Tobias17} While lack of insurance coverage is associated with adverse health outcomes for all children, it is particularly significant for children with chronic conditions requiring ongoing subspecialty care, including children with CHD. Expanding public insurance coverage may assist in minimising the likelihood of coverage gaps for this vulnerable population.

Uniquely among studies assessing quality of life or health outcomes among children with CHD, we found that family food stamp programme participation was associated with increased likelihood of activity limitation. Previous studies have found that children who live in food insecure households report lower quality of life, ^{Reference Casey, Szeto and Robbins18} and the American Academy of Pediatrics recommended in 2015 that paediatricians should screen for food security at health maintenance visits. ¹⁹ This screening remains limited in paediatric practices, with only 15% of paediatricians in a variety of specialties conducting regular screening for food insecurity. ^{Reference Barnidge, LaBarge, Krupsky and Arthur20} Future studies should analyse the feasibility and utility of food insecurity screening in specialty clinics, like paediatric cardiology, to address the needs of patients seen in these clinics who are at high risk for food insecurity. This work could build on successful initiatives in primary care settings to identify and address food insecurity though a combination of enrolment in needs-based programmes and referral to community resources, such as food banks. ^{Reference De Marchis, Torres and Benesch21}

Neurodevelopmental impairments associated with early surgery for CHD can lead to deficits in educational performance in later childhood, with one study reporting that children with CHD performed below average on literacy and mathematics in standardised state exams. ^{Reference Mulkey, Swearingen and Melguizo22} Furthermore, family socio-economic status disadvantage was associated with poorer neurodevelopmental outcomes among children with CHD in another study. ^{Reference Bellinger, Wypij and Rivkin23} Children with CHD are more likely to receive special education services than children without CHD, as they experience difficulty in learning, concentration, communication, self-care, and delays in gross and fine motor skills. ^{Reference Razzaghi, Oster and Reffhuis2,Reference Farr, Downing, Riehle-Colarusso and Abarbanell5} Furthermore, children with CHD are also three times more likely than children without CHD to miss 10 more days of school in the past 12 months. ^{Reference Razzaghi, Oster and Reffhuis2,Reference Farr, Downing, Riehle-Colarusso and Abarbanell5} However, our study did not find that school absences among children with CHD were associated with family socio-economic status or other child or family characteristics. Children who miss school may have more severe disease with residual defects requiring frequent paediatric cardiology follow-up visits, or may have schooling interrupted by hospitalisations or non-elective surgical interventions.

Apart from our analysis of missed school days, it is also important to note that multiple potential associations between socio-economic status and health-related outcomes did not reach clinical or statistical significance in our study. For example, in our analysis of general caregiver-rated health, several important indicators such as poverty status, insurance type, and food stamp programme participation were not associated with this outcome. At least two mechanisms may be responsible for limiting the association between socio-economic status and the outcomes in our study. First, there may be survivorship bias where the most disadvantaged children with CHD have the highest mortality risk in infancy and may not have survived to be included in the NHIS sampling frame. Second, increased contact with the healthcare system among children with CHD (compared to children without CHD) may have helped address health problems in this population that would have demonstrated a stronger socio-economic gradient in a sample of all children. We also note that aside from differences according to socio-economic characteristics, our analysis found notable racial disparities in the health status of children with CHD. This finding was similar to studies that have examined the significance of racial disparities in healthcare outcomes among infants with CHD. ^{Reference Peyvandi, Baer and Moon-Grady10} In the NHIS sample, non-Hispanic black children tended to have worse caregiver-rated health, were more likely to require specialised equipment, and were more likely to be enrolled in special education than white children with CHD. Therefore, further attention to equity in the health and functional status of children with CHD must consider both socio-economic and racial disparities in outcomes in this patient population.

Though our study presents novel information on the association between socio-economic status and health-related outcomes in a population-based sample of children with CHD, our conclusions are limited by some aspects of the data and analytic approach. First, the National Health Interview Survey questionnaires address a number of important social determinants of health, but does not capture other potentially relevant factors, such as transportation access and health literacy. Considering differences by health insurance coverage, it is possible that some patients with private coverage had greater barriers to accessing care than patients with public or other coverage, due to cost-prohibitive copays. Furthermore, the National Health Interview Survey does not contain granular information on the type or severity of the defect, or pertinent medical and surgical history that may help distinguish between CHD and other cardiac problems. With only one child chosen per family for completion of the detailed health questionnaire, it is possible that the survey missed additional children with CHD living in the same family. Our weighted estimate of the number of children with CHD is lower than published estimates reporting up to 1 million United States of America children live with CHD. ²⁴ This may be because minor or surgically corrected CHD may be under-reported by caregivers responding to the survey. Caregiver responses to survey questions were subjective, so interpretation of outcomes such as general health status could be affected by the respondent’s educational attainment and health literacy. Additionally, the psychometric properties of outcome measures (especially the general health question) could not be analysed in this study. A more granular primary outcome measure may have revealed greater disparities by socio-economic status. Lastly, the National Health Interview Survey was intended to provide nationally representative estimates, but the public-use data from this survey could not be subset to examine state-level differences in socio-economic status or health-related outcomes.

Our analysis demonstrates that family characteristics and in particular socio-economic status are associated with several outcomes for children with CHD. Children with CHD who lacked public or private health insurance or whose families participated in the food stamp programme were at increased risk for functional limitation and need for special education services, although these characteristics were not consistently associated with all outcomes examined. Additionally, we identified significant disparities between black and white children in a range of health and functional status outcomes. From a medical standpoint, we have achieved great success in outcomes, morbidity and mortality as evidenced by the fact that many of these CHD patients are living well into adulthood. It is of utmost importance to provide holistic care for this population and identify socio-economic factors that may be associated with poor health and development, in order to deliver appropriate interventions and further improve outcomes. Additional research is needed to elucidate the role of these factors, which may not be routinely captured in paediatric cardiology follow-up care.