Abstract
Background:
Although cardiac rehabilitation (CR) has established benefits for cardiovascular health, it remains significantly underutilized, with substantial differences in participation related to factors such as educational attainment (EA), race, and ethnicity. We studied a geographically and racially diverse cohort of insured individuals in a health claims database to (1) evaluate differences in CR participation by EA and race or ethnicity and (2) assess how EA modifies associations between race or ethnicity and CR participation.
Methods:
We conducted a retrospective cohort study of individuals identified in Optum’s de-identified Clinformatics® database between 1/1/2016 and 12/31/2019. Eligible individuals included those aged ≥18 years with a hospitalization for an incident CR-qualifying diagnosis. We calculated incidence rates of CR enrollment by EA and race or ethnicity, as well as associations of EA and race or ethnicity with CR enrollment, and evaluated interaction between EA and race or ethnicity with respect to CR participation.
Results:
We identified 171,297 individuals eligible for CR with a mean±SD age of 70.4±11.6 years; 37.4% were female, and 68.3% had > high school education. We observed a dose-response association between EA and rate of participation in CR. After adjustment, compared to White individuals, the odds of attending CR was 24% lower for Asian individuals [95% confidence interval (CI): 17%, 30%], 13% lower for Black individuals (95% CI: 9%, 17%), and 32% lower for Hispanic individuals (95% CI: 28%, 35%), all p<0.0001. However, Black individuals with ≥bachelor’s degree had a similar odds of CR enrollment as White individuals with ≥bachelor’s degree (odds ratio 1.01, 95% CI: 0.85, 1.20, p=0.95).
Conclusions:
EA was positively associated with CR enrollment across racial and ethnic groups. Higher EA might partially attenuate racial and ethnic differences in CR participation, but significant disparities persist. Our findings support increased attention to individuals with limited education to improve CR enrollment.
Keywords: Cardiac rehabilitation, Educational attainment, Race, Ethnicity, Disparities
Graphical Abstract
INTRODUCTION
Cardiac rehabilitation (CR) is a multidisciplinary, evidence-based program for the secondary prevention of cardiovascular disease and is associated with improvements in quality of life, morbidity, and mortality [1]. However, despite national guidelines supporting the use of CR and common coverage for CR with health insurance plans, the majority of eligible patients do not participate.
There remain significant differences in CR participation by educational attainment (EA) [2,3], as well as by race or ethnicity [4,5], even among those with high income [6]. Furthermore, although higher EA is associated with improved health outcomes, the protective effects of EA differ relative to race or ethnicity [7].
In this study, we investigated the association of race or ethnicity and EA with CR enrollment in a cohort of insured individuals who qualified for CR. We then assessed the association between race or ethnicity and CR enrollment by EA. We hypothesized that EA would be positively associated with CR enrollment among all races and ethnicities; given the strong association of EA and health literacy with health behaviors [7,8], we further hypothesized that higher EA would attenuate racial and ethnic differences in CR participation.
METHODS
Data Source
We utilized health claims data from Optum’s Clinformatics® Data Mart database. Optum is an administrative database that includes de-identified inpatient, outpatient, emergency department, pharmacy, and laboratory health claims from individuals with either a commercial health insurance plan or Medicare Advantage (C and D). The database is updated annually and contains a geographically and socially diverse sample. The University of Pittsburgh Institutional Review Board classified this study as exempt from human subjects research review given its use of pre-existing, de-identified data.
Inclusion/Exclusion Criteria
We identified individuals ≥18 years of age who were eligible for CR between January 1, 2016 and December 31, 2019. CR-qualifying events were hospitalization for acute myocardial infarction, coronary artery bypass grafting, heart valve repair/replacement, or percutaneous coronary intervention; each event was identified by specified diagnostic codes linked to each encounter. For individuals with more than one primary qualifying event, the highest priority code defined the index event. Eligible individuals had continuous enrollment at least 6 months prior to and 90 days following their incident qualifying event. We excluded individuals discharged to a skilled nursing facility or long-term care facility, and those with missing data on race or ethnicity, sex, or EA. Online Figure 1 presents the flow diagram for cohort selection and ascertainment.
Ascertainment of Variables
Information on EA was derived using nine-digit ZIP codes in combination with US Census data and provided by Clinformatics®. We then categorized EA as high school diploma or less, some college, or bachelor’s degree or greater. Race or ethnicity were categorized as Asian, Black, Hispanic, or White using publicly available data or imputed with a previously described and validated algorithm utilizing individuals’ names and nine-digit ZIP codes [9]. The primary outcome was enrollment in CR within 1 year of the qualifying index event, as defined by current procedural terminology codes.
Age and sex were defined by the database. Annual household income was derived from estimates of average household income at the nine-digit ZIP code level and validated with self-reported surveys. Comorbidities were defined using ICD codes and were used to calculate the Elixhauser Comorbidity Index, a validated method for measuring the impact of overall comorbidity burden [10].
Statistical Analysis
We calculated descriptive statistics of baseline characteristics among all CR-eligible individuals by categories of EA. We determined incidence rates of CR enrollment across all combinations of EA and race or ethnicity, incorporating person-years of observation. We then examined associations of EA and race or ethnicity with CR enrollment in multivariable logistic regression models, with adjustment for age, sex, comorbidities, qualifying event, annual income, insurance type, and geographic region. We also stratified these models by EA to evaluate possible effect modification. An a-priori two-sided alpha of <0.05 was considered statistically significant. All analyses were conducted using SAS version 9.4 (Cary, NC, USA).
RESULTS
Our final analytic sample included 171,297 individuals with a mean±SD age of 70.4±11.6 years; 37.4% were female (Table 1). Most were White race (75.0%) and 68.3% received at least some college education.
Table 1.
Sociodemographic and clinical characteristics of patients eligible for cardiac rehabilitation, by educational attainment.
| Variable | Overall N = 171,297 | Educational Attainment |
||
|---|---|---|---|---|
| ≤ High School Diploma n = 54,269 (31.7%) | Some College n = 93,893 (54.8%) | ≥ Bachelor’s Degree n = 23,135 (13.5%) | ||
|
| ||||
| Demographics | ||||
| Age (years), mean ± SD | 70.4 (11.6) | 69.6 (11.3) | 70.8 (11.5) | 71.1 (12.3) |
| Female sex, n (%) | 64125 (37.4%) | 21921 (40.4%) | 34719 (37.0%) | 7485 (32.4%) |
| Race or ethnicity, n (%) | ||||
| Asian | 4565 (2.7%) | 870 (1.6%) | 2396 (2.6%) | 1299 (5.6%) |
| Black | 19987 (11.7%) | 10647 (19.6%) | 8426 (9.0%) | 914 (4.0%) |
| Hispanic | 18272 (10.7%) | 9006 (16.6%) | 7864 (8.4%) | 1402 (6.1%) |
| White | 128473 (75.0%) | 33746 (62.2%) | 75207 (80.1%) | 19520 (84.4%) |
| Household income, n (%) | ||||
| <$40,000 | 52835 (30.8%) | 27646 (50.9%) | 23389 (24.9%) | 1800 (7.8%) |
| $40,000–49,999 | 15743 (9.2%) | 6768 (12.5%) | 8331 (8.9%) | 644 (2.8%) |
| $50,000–59,999 | 16307 (9.5%) | 6073 (11.2%) | 9288 (9.9%) | 946 (4.1%) |
| $60,000–74,999 | 19926 (11.6%) | 5156 (9.5%) | 12849 (13.7%) | 1921 (8.3%) |
| $75,000–99,999 | 25618 (15.0%) | 4020 (7.4%) | 17888 (19.1%) | 3710 (16.0%) |
| ≥$100,000 | 33490 (19.6%) | 1520 (2.8%) | 18589 (19.8%) | 13381 (57.8%) |
| Unknown | 7378 (4.3%) | 3086 (5.7%) | 3559 (3.8%) | 733 (3.2%) |
| CR qualifying diagnosis, n (%) | ||||
| Myocardial Infarction | 99443 (58.1%) | 33101 (61.0%) | 54143 (57.7%) | 12199 (52.7%) |
| CABG | 23735 (13.9%) | 7374 (13.6%) | 13132 (14.0%) | 3229 (14.0%) |
| Valve repair/replacement | 32309 (18.9%) | 8195 (15.1%) | 18391 (19.6%) | 5723 (24.7%) |
| PCI/stent | 72243 (42.2%) | 23622 (43.5%) | 39501 (42.1%) | 9120 (39.4%) |
| Insurance type, n (%) | ||||
| Commercial | 40523 (23.7%) | 11112 (20.5%) | 22420 (23.9%) | 6991 (30.2%) |
| Medicare | 106115 (62.0%) | 29524 (54.4%) | 61603 (65.6%) | 14988 (64.8%) |
| Low-income | 15918 (9.3%) | 8844 (16.3%) | 6385 (6.8%) | 689 (3.0%) |
| Medicare + Medicaid | 8741 (5.1%) | 4789 (8.8%) | 3485 (3.7%) | 467 (2.0%) |
| Elixhauser Comorbidity Index, median (25th, 75th) | 7 (4, 10) | 7 (5, 10) | 7 (4, 10) | 6 (4, 9) |
| Follow-up time (months), median (25th, 75th) | 29.6 (18.4, 43.4) | 28.4 (16.5, 42.3) | 30.1 (19.1, 43.8) | 30.7 (20.9, 44.1) |
CABG, coronary artery bypass graft; CR, cardiac rehabilitation; PCI, percutaneous coronary intervention.
Overall, 26.7% of all qualifying individuals enrolled in CR. The incidence rate of CR enrollment per 1000 person-years among individuals with ≥ bachelor’s degree was highest at 130.6 (95% CI: 127.8, 133.5) enrollments, compared to 109.9 (95% CI: 108.6, 111.2) for individuals with some college education and 76.1 (95% CI: 74.6, 77.6) in those with ≤ high school diploma (Online Table 1). Compared to individuals with ≥ bachelor’s degree, those with some college education had an adjusted 14% lower odds (OR=0.86, 95% CI: 0.83, 0.90, p<0.0001) and those with ≤ high school education had an adjusted 35% lower odds (OR=0.65, 95% CI: 0.62, 0.68, p<0.0001) of enrolling in CR.
In the analysis stratified by EA (Table 2), the associations between race or ethnicity and CR enrollment varied by EA (p, interaction<0.0001). For example, among those with ≤ high school diploma, Asian individuals had a 36% lower odds of attending CR than White individuals (OR=0.64, 95% CI: 0.50, 0.81, p=0.0001), whereas among those with ≥ bachelor’s degree, this association was attenuated to a 17% lower odds of participation (OR=0.83, 95% CI: 0.72, 0.96, p=0.01).
Table 2.
Association between race or ethnicity and participation in cardiac rehabilitation, by educational attainment.
| Asian n = 4565 (2.7%) |
Black n = 19987 (11.7%) |
Hispanic n = 18272 (10.7%) |
White n = 128473 (75.0%) |
||||
|---|---|---|---|---|---|---|---|
|
|
|
|
|||||
| ORa (95% CI) | p | ORa (95% CI) | p | ORa (95% CI) | p | — | |
|
|
|
||||||
| Overall | 0.76 (0.70, 0.83) | <0.0001 | 0.87 (0.83, 0.91) | <0.0001 | 0.68 (0.65, 0.72) | <0.0001 | Ref |
| ≤ High School Diploma | 0.64 (0.50, 0.81) | 0.0001 | 0.96 (0.90, 1.03) | 0.25 | 0.66 (0.61, 0.72) | <0.0001 | Ref |
| Some College | 0.76 (0.67, 0.85) | <0.0001 | 0.78 (0.73, 0.83) | <0.0001 | 0.69 (0.64, 0.74) | <0.0001 | Ref |
| ≥ Bachelor’s Degree | 0.83 (0.72, 0.96) | 0.01 | 1.01 (0.85, 1.20) | 0.95 | 0.73 (0.63, 0.85) | <0.0001 | Ref |
CI, confidence interval; OR, odds ratio.
From logistic regression models with adjustment for age, sex, comorbidities, qualifying event, annual income, insurance type, and geographic region.
Figure 1 highlights the odds of attending ≥1 CR sessions, with adjustment for sociodemographic and clinical covariates and stratified by both race or ethnicity and EA. Across all racial and ethnic groups, we observed a positive dose-response association between EA and CR enrollment. Relative to White individuals with ≥ bachelor’s degree, differences in CR participation were greatest among Asian and Hispanic individuals with ≤ high school education, for whom Asian individuals had a 59% lower odds (OR=0.41, 95% CI: 0.32, 0.52, p<0.0001) and Hispanic individuals a 57% lower odds (OR=0.43, 95% CI: 0.39, 0.47, p<0.0001) of enrolling in CR. Compared to White individuals with ≥ bachelor’s degree, the only group that did not have a significantly lower odds of CR participation was Black individuals with ≥ bachelor’s degree (OR=1.01, 95% CI: 0.85, 1.20, p=0.95).
Figure 1.
Association between educational attainment and cardiac rehabilitation enrollment, by race or ethnicity.
The figure shows the likelihood of cardiac rehabilitation participation by educational attainment, stratified by race or ethnicity. Individuals of White race and ≥ bachelor’s degree serve as the referent with 95% confidence intervals represented by brackets. Estimates are from logistic regression models with adjustment for age, sex, comorbidities, qualifying event, annual income, insurance type, and geographic region.
DISCUSSION
In this large contemporary sample of insured individuals, EA was positively associated with CR enrollment across racial and ethnic groups. Compared to White individuals with the highest EA, CR attendance was lowest among Asian and Hispanic individuals with the lowest EA. We observed an attenuation of racial differences in CR enrollment with increasing EA in Asian individuals, and to a smaller degree in Hispanic individuals. Associations in Black individuals were less clear, although Black individuals with an EA of ≥ bachelor’s degree had similar odds of CR enrollment as White individuals with the same EA.
Our finding of a positive association between EA and CR enrollment is consistent with prior research [2,3]. EA is associated with visits to preventative care appointments, partly through differences in occupation and access to care [11]. Limited social resources, including income, healthcare coverage, and transportation – all of which are linked to EA -- have important implications for cardiovascular health [7], and may pose a barrier to CR enrollment. Higher EA also increases health literacy, which is associated with cardio-protective behaviors, disease knowledge, and self-management [8,12].
We also observed significant differences in CR enrollment by race or ethnicity, consistent with prior evidence [4–6]. However, studies of the interaction between EA and race or ethnicity in CR participation are scarce. We found an attenuation of the racial and ethnic differences in CR participation in Asian and (to a lesser extent) Hispanic individuals with increasing EA.
Associations for Black individuals were less consistent; however, among those with the highest EA, Black individuals had similar odds of attending CR as White individuals. Our results suggest that additional factors, such as referral to CR, access to transportation, competing priorities, and language discordance may contribute to the differing associations of higher EA with CR enrollment by race or ethnicity [4,13].
Our findings have important implications for patient care. Lower EA may identify patients who are less likely to enroll in CR and who are at increased risk for poor health outcomes. In patients with lower EA, efforts to improve health literacy and overcome social barriers to CR enrollment may increase participation [14]. In addition, our findings of the possible intersection between EA and race or ethnicity may help to further guide policies and allocation of resources to overcome factors that impede CR enrollment [4,13], and to possibly inform the development of novel CR delivery methods such as home-based CR [15]. Because EA is strongly and consistently linked to cardiovascular risk factors, health behaviors, and clinical outcomes [7], strategies to equitably increase EA may represent one potential approach to mitigate racial and ethnic disparities in cardiovascular health.
Strengths of our study include the use of a large and diverse cohort with a mix of qualifying diagnoses for CR. Furthermore, we were able to adjust for a variety of covariates that may influence CR enrollment.
Our study has several limitations. First, we cannot exclude residual confounding by unmeasured variables that might influence CR participation, such as social resources or transportation. Second, we were unable to determine from administrative coding whether patients were referred to CR but elected not to attend. Third, our study only included patients who enrolled in commercial insurance or Medicare Advantage, limiting generalizability. Finally, erroneous coding of administrative claims data is a possibility. However, our sample size, consistent results, and precision of estimates are reassuring in this regard.
In conclusion, we identified positive associations between EA and CR enrollment across race or ethnicity. Higher EA may partially attenuate racial and ethnic differences in CR participation, but significant disparities remain. Future studies should investigate additional factors that may contribute to disparities in CR participation.
Supplementary Material
Highlights.
Education is positively associated with enrollment in cardiac rehabilitation
Substantial racial and ethnic disparities in cardiac rehabilitation enrollment
Education may partially attenuate racial and ethnic disparities
SOURCES OF FUNDING
Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health (Bethesda, MD) under Award Number T32GM008208. Dr Magnani is supported by NIH awards R01HL14301, R33HL144669, R01HL160749, and K24HL160527. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
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