Congenital heart defects (CHDs) are common among infants born with Down syndrome (DS), with almost half of all infants with DS also having CHDs (Santoro and Steffensen 2021). Survival to adulthood has increased for individuals with CHDs (Moons et al. 2010; Downing et al. 2023) and individuals with DS (Centers for Disease Control and Prevention 2001; Englund et al. 2013) over the years, resulting in an increasing population of adults with CHDs and DS who may have unique health challenges and healthcare needs. Some evidence exists that adults with DS in general have lower rates of arterial hypertension (Morrison et al. 1996), myocardial infarction, and heart disease (Alexander et al. 2016), but higher rates of stroke (Sobey et al. 2015), pulmonary hypertension, diabetes (Alexander et al. 2016), and sleep apnea (Maris et al. 2016; Capone et al. 2018). The few existing studies assessing these outcomes in individuals with DS and CHDs have been based on children (Frid et al. 2002; Dawson et al. 2014) or hospitalizations (Baraona et al. 2013). Clinical guidelines exist (Tsou et al. 2020) for individuals with DS but are based mainly on expert opinion with limited scientific evidence. The guidelines contain only one weak recommendation specific to adults with DS and CHDs: periodic cardiac evaluation due to the increased risk of stroke. It is not well understood how commonly adults with CHDs and DS receive appropriate cardiac and non-cardiac healthcare and what comorbidities they most frequently experience throughout their lifespan.

Therefore, the objective of this study was to assess the prevalence of comorbidities and healthcare utilization among adults with CHDs and DS using data from the Congenital Heart Survey to Recognize Outcomes, Needs, and well-beinG (CH STRONG). This information may be used to inform clinical care guidelines and optimize the management of comorbidities for adults with CHDs and DS.

Of the 1656 CH STRONG respondents, 50 (3.0%) were missing demographic and healthcare characteristics, and 106 (6.4%) were missing data on comorbidities or healthcare utilization outcomes (Table S2). Therefore, the final analytic sample included 1500 (90.6%) respondents with complete data (representing 17.8% of the CH STRONG eligible population), of whom 9.1% had a DS diagnosis.

Over a third (38.7%) of adults with CHDs and DS had severe CHDs, which did not differ compared to those without DS (33.8%) (Table 1). The three most common primary CHDs among respondents with DS were atrioventricular (AV) canal/endocardial cushion defect (32.8%), atrial septal defect (ASD) (26.3%), and ventricular septal defect (VSD) (21.2%), while among those without DS were VSD (27.6%), multiple primary CHDs (13.4%), and ASD (9.0%). Comparing respondents with DS to those without, the distributions of non-severe CHD type (shunt: 56.2% vs. 41.6%), age (< 25 years old: 51.8% vs. 42.7%), sex (male: 55.5% vs. 45.0%), race/ethnicity (Hispanic: 16.1% vs. 10.1%), and insurance (any public health insurance: 77.4% vs. 22.8%) differed (p < 0.05 for all). Additionally, respondents with DS were more likely to have their survey completed by a proxy (91.2% vs. 13.2%, p < 0.0001).

Among adults with CHDs, 5.5% of those with DS had one or more cardiac comorbidities compared to 14.2% of those without DS (aPR = 0.27 [0.13–0.55], Figure 1, Table S3), with the most notable difference in reported hypertension, which was lower for adults with DS. Prevalence of having one or more non-cardiac comorbidities was 26.7% in adults with CHDs and DS, similar to that among adults without DS (21.2%). However, there was a 3.7 times increased prevalence of sleep apnea in adults with DS (13.7% vs. 3.2%). Among adults with DS, 22.8% had one visit with a healthcare provider in the past 12 months (aPR = 1.48 [1.11–1.97]), and 64.2% had between 2 and 7 visits (aPR = 1.16 [1.06–1.27]). Approximately one in five adults with DS reported ER visits in the past year (aPR = 0.57 [0.42–0.78]), 6.2% reported hospital admissions overall (aPR = 0.56 [0.33–0.95]), 0.7% reported cardiac-related hospital admissions (aPR = 0.16 [0.04–0.65]), and 1.2% reported delays in care due to cost during the 12 months before the survey (aPR = 0.14 [0.04–0.42]) (Figure 2, Table S3). No other associations were found.

Prevalence estimates were similar, and associations remained when analyses were limited to individuals < 25 years old, 25–30 years old, > 30 years old, with health insurance, with a shunt CHD, with a primary diagnosis of ASD, VSD, or AV canal/endocardial cushion defect, with any diagnosis of ASD, VSD, or AV canal/endocardial cushion defect, with severe CHD, after adjusting for proxy report, and when imputing to account for missing data (Tables S4–S13). However, for most sensitivity analyses, CIs were wider due to lower sample sizes and reduced power, and some aPRs could not be calculated due to insufficient data. Imputing data did not change the estimated aPRs by more than eight-hundredths of a decimal.

Our findings indicate that DS is common among young adults with CHDs—over 9% of young adults with CHDs in the general population are also diagnosed with DS. Previous studies estimated the prevalence to be between 5% and 8%; however, these studies were among children requiring cardiac operations or individuals of all ages receiving CHD-related healthcare (Reller and Morris 1998; Evans et al. 2014; Glidewell et al. 2021). This analysis is one of the first to assess comorbidities and healthcare utilization among adults with CHDs and DS in the U.S. We found that one in four adults with CHDs and DS had a non-cardiac comorbidity, similar to adults with CHDs without DS, and about one in 20 had cardiac comorbidities, an estimate 75% lower than that of adults with CHDs without DS. Adults with CHDs and DS were less likely to report ER visits and hospital admissions in the last 12 months. They also reported fewer delays in care due to cost and more visits with a healthcare provider in the last 12 months. These findings persisted when stratified by CHD severity, CHD type, age group, health insurance status, when adjusted for proxy report, and when multiple imputation was used to account for non-response. Overall, these results show that adults with CHDs and DS comprise a substantial percentage of adults with CHDs and have a unique demographic and health profile, even when compared to adults with the same CHD types.

Some evidence suggests that cardiac and non-cardiac outcomes differ among the general population of individuals with and without DS; however, most studies have not stratified results by CHD status. Adults with DS are more likely than those without DS to experience low blood pressure (Morrison et al. 1996); and, among young adults with CHD, we similarly found a lower prevalence of hypertension. Studies have also shown that rates of myocardial infarction and heart disease are the same or lower in individuals with DS compared to those without (Tsou et al. 2020); similar to our findings among individuals with CHD. Strokes may occur more often and at younger ages in individuals with DS; however, we found no difference by DS status in the low prevalence of stroke in young adults with CHD. A previous study of hospitalized patients (Sobey et al. 2015) found higher prevalence of diabetes and sleep apnea among adults with DS, compared to those without DS; similarly, our findings in adults with CHD showed sleep apnea was over three times higher in adults with DS than those without, however, the prevalence of diabetes did not differ statistically.

Our results also show that those with DS have better healthcare access, and insurance status may partly explain this finding. A previous study assessing Medicaid enrollment and service use among adults with DS found that, compared to adults without developmental disabilities, adults with DS were more consistently enrolled in Medicaid (Rubenstein et al. 2023). Similarly, in our study, adults with CHDs and DS were more likely to have some form of public health insurance compared to adults with CHDs without DS and were less likely to report delaying care due to cost. Additionally, a higher proportion of adults with CHDs and DS in CH STRONG reported multiple visits with a healthcare provider in the past year, which may indicate better access to care, compared to adults with CHDs without DS. Little information exists on the receipt of cardiology care among adults with DS and CHDs. A study based on Medicaid data found that over 90% of adolescents and adults with CHDs and DS had an echocardiogram in a 5-year period between 2006 and 2010 (Jensen et al. 2021). Our study found that only half of the adults with CHDs and DS had seen a cardiologist in the last 2 years and over a third were LTF for cardiology care based on their specific CHDs, similar to adults with CHDs without DS. These results suggest that a large percentage of individuals with CHDs, including those with DS, are not receiving the recommended routine cardiac evaluation to improve their cardiac health and decrease their risk of stroke (Tsou et al. 2020; Stout et al. 2019).

Compared to U.S. adults with CHDs without DS, our findings suggest that adults with CHDs and DS had lower rates of hospitalization—about half that of adults with CHD without DS. Our findings add to those of an older U.S. study (Baraona et al. 2013) of admissions for adults with CHDs occurring from 1998 to 2009, which found that hospitalizations of adults with CHDs and DS represented a decreasing proportion of admissions, were less likely to include cardiac procedures or surgery, and had lower hospital charges compared to adults with CHDs without DS.

Previous studies have also noted similar or better health-related outcomes, such as survival, when comparing individuals with CHDs and DS to those with CHDs without DS. Among individuals with CHD born 1980–1997, the underlying population for CH STRONG, 85.1% of infants born with CHD and DS survived to 25 years of age, which was similar to the 83.2% of infants born with CHD and no genetic syndromes (Downing et al. 2024). A previous study assessing in-hospital death among children undergoing surgery for CHDs found that children with DS were more likely to survive to discharge than children without DS, though there were specific procedures (i.e., placement of a systemic to pulmonary shunt, the bidirectional Glenn shunt procedure) that resulted in higher mortality for children with DS (Evans et al. 2014). Additionally, among a cohort of individuals undergoing congenital heart surgery identified in a national clinical database, those with DS were not at increased risk of post-surgical mortality, although they had a prolonged length of inpatient stay associated with respiratory infection complications (Fudge Jr et al. 2010). These studies have speculated that similar or better survival outcomes may be associated with subtle differences in cardiac structure between individuals with DS and those without (Evans et al. 2014; Fudge Jr et al. 2010). In our study, limiting the analysis to individuals with ASD, VSD, and AV canal/endocardial cushion defect did not impact the results, yet differences in CHDs between groups may still exist. Another study examining longer-term survival of children with CHDs and DS after congenital heart surgery found that DS was a predictor for 30-year all-cause mortality, but not a predictor of CHD-related mortality, possibly due to other co-occurring conditions (Peterson et al. 2021).

It is possible that diagnostic overshadowing (the misattribution of signs and symptoms of a comorbid condition to an underlying disability) or differences in self-identification of symptoms may contribute to lower rates of reported comorbidities in adults with CHD and DS. However, it is unknown how often diagnostic overshadowing may occur for people with DS.

Individuals with DS make up a substantial proportion of young adults with CHDs and have unique health outcomes and patterns of healthcare utilization. In this study among young adults with CHDs and DS, one in 20 had cardiac comorbidities, one in four had non-cardiac comorbidities, and they had low rates of cardiology care. Cardiac comorbidities, ER visits, and hospitalizations for adults with CHDs and DS differed from those with CHDs without DS, possibly as a result of differences in insurance status and access to care. Differences in CHD type among adults with DS may also impact outcomes, although this was not found in our study. Continued understanding of the needs of people with CHDs and DS may inform clinical guidelines, ensure that their health needs are met throughout their lifespan, and help individuals, their families, and caregivers plan for the future.