Social Inequality in the Comprehensive Cardiac Rehabilitation Pathway: A Nationwide Cohort Study Across Hospitals and Primary Health Care Centers

Abstract

Purpose:

To examine socioeconomic differences in the nonpharmacological cardiac rehabilitation (CR) pathway from hospital discharge to CR completion in hospital and primary care settings.

Methods:

This nationwide cohort study included patients hospitalized with ischemic heart disease between April 1, 2019, and March 31, 2022. Follow-up continued through December 31, 2022, focusing on nonutilization of 11 CR components, including: delayed CR needs assessment (>14 days) and physical exercise training (>29 days); lack of patient education, physical exercise training, test of cardiorespiratory fitness (CRF), depression screening, improvement in CRF (<10% increase), smoking cessation, and finalizing CR meeting; and completion of <75% of planned exercise sessions and dropout. Socioeconomic differences were analyzed by educational attainment, income, occupation, and cohabitant status.

Results:

Among 45 497 hospitalized patients with ischemic heart disease, 43% (n = 19 573) participated in CR. Only 25% received a CR needs assessment within 14 days of discharge. Socioeconomic differences were demonstrated throughout the CR pathway, except for the finalizing meeting, improvement in CRF, and smoking cessation. The odds of nonutilization among patients with lower educational attainment ranged between 8% higher odds of delayed CR needs assessment (adjusted OR = 1.08: 95% CI, 1.01-1.15) and 31% higher odds of no CRF test (adjusted OR = 1.31: 95% CI, 1.18-1.45).

Conclusions:

The observed socioeconomic differences throughout the CR pathway underscore the need for targeted interventions to ensure early assessment of CR needs and participation in specific CR activities among patients with lower socioeconomic positions. This study identifies specific patient characteristics and CR activities as key markers for reducing these inequalities.

This nationwide cohort study of 45,497 patients with ischemic heart disease demonstrates socioeconomic differences in the utilization of 11 core components of the cardiac rehabilitation (CR) pathway across hospitals and primary health care centers. It identifies patient characteristics and CR activities as potential targets for interventions aimed at reducing social inequality.

KEY PERSPECTIVE:

What is novel?

• Using nationwide population-based information to identify patients hospitalized with ischemic heart disease, this study tracks patients through the full nonpharmacological cardiac rehabilitation (CR) pathway, including services delivered in both hospitals and primary health care centers.

• The study reports a 43% CR participation rate and substantial variability in the use of 11 CR components.

• Patients with indicators of lower socioeconomic position had statistically significantly higher odds of delayed CR assessment, nonutilization of patient education and physical exercise training, completing less than 75% of the planned exercise sessions, no test of cardiorespiratory fitness, and no depression screening.

What are the clinical and/or research implications?

• Targeted clinical interventions are needed for mitigating socioeconomic differences in the CR pathway, and this study identifies specific patient characteristics and CR activities as key markers for reducing these inequalities.

• Given that early CR enrollment likely enhances CR participation and improves cardiovascular outcomes, this study identifies socioeconomic differences in the early assessment of CR needs as a critical target for reducing inequalities.

Cardiac rehabilitation (CR) is a class 1A recommendation for secondary prevention of ischemic heart disease (IHD).^1,2 Despite proven benefits,^1,2 participation rates remain below 50%,^3-5 with pronounced disparities in enrollment.^4-7 Socioeconomic differences in the receipt and timing of nonpharmacological CR activities (hereafter referred to as CR) within the CR pathway are less well understood.^8,9

Cardiac rehabilitation is a multidisciplinary intervention aimed at optimizing the patient functioning, cardiovascular risk reduction, and healthy behaviors such as medication adherence and self-management.^1,2,10,11 Early enrollment in CR, ideally within 1 to 2 weeks after the qualifying event, improves participation^12,13 and cardiovascular outcomes.¹⁴ Core CR components include exercise training, patient education, tobacco cessation, nutritional counselling (not assessed in this study), and psychosocial management.^1,2 Physical exercise, healthy diet, weight control, and smoking cessation are proven effective in improving the cardiovascular risk profile and clinical outcomes.^1,15 While the evidence for psychological interventions¹⁶ and patient education¹⁷ is less definitive, it suggests a moderate increase in health-related quality of life. A review of 148 trials implies that the combination of CR core components is essential, with psychosocial management, exercise training, and patient education being particularly crucial in reducing mortality and myocardial infarction.¹⁸

Social determinants of health are increasingly recognized as key drivers of health disparities, in part due to unequal access to health care.^2,19 Patients with lower socioeconomic position enter CR with higher cardiovascular risk profiles²⁰ but have lower CR uptake.¹⁹ The disparities include risk factors that are modifiable by CR, such as unfavorable cardiorespiratory fitness (CRF), physical function, body mass index, lipid profiles, smoking status, comorbidities, depressive symptoms, and medication adherence.^20-22 Evidence on socioeconomic differences in the utilization of specific CR components⁸ and in dropout in nonhospital settings^4-7 remains limited. Such insights are crucial for guiding targeted interventions and promoting adherence to preventive therapies.¹¹ This study examined socioeconomic differences throughout the comprehensive CR pathway among patients with IHD.

METHODS

This nationwide population-based cohort study included all patients ≥18 years diagnosed with IHD in the hospital from April 1, 2019 to March 31, 2022. Follow-up on nonutilization of phase II CR components in hospitals and community health care centers continued until December 31, 2022. Data from national databases were linked via the unique personal identification number assigned to all Danish residents.^23-28 The Danish welfare system authorizes registration in nationwide databases of tax-financed services within the universal health care, education, and social welfare (eg, pension and unemployment insurance). Patients with IHD have free access to hospital care and CR.²³ The study complies with the Strengthening the Reporting of Observational Studies in Epidemiology guidelines for cohort studies to enhance transparency in reporting.²⁹

SETTING AND PARTICIPANTS

Phase II CR in Denmark is initiated after the index hospitalization and delivered in hospitals and community health care centers in accordance with international clinical guidelines.^11,30 Hospitals are responsible for the initial CR needs assessment, evaluating cardiovascular risk factors, clinical status, pharmacological therapy, exercise risk, psychosocial factors, and health literacy, as a gateway to CR referral and uptake. Hospitals initiate and optimize pharmacological therapy, which is subsequently managed in general practice, and community health care centers increasingly deliver the remaining CR components.^7,28 This study assessed 11 CR components, as detailed in the Supplemental Digital Content 1, Table A, available at: https://links.lww.com/JCRP/A673. A CR pathway was defined as all CR activities occurring within 1 year of each other; initiation beyond 1 year constituted a new CR pathway. Since 2015, all Danish hospitals are mandated to register CR in the Danish Cardiac Rehabilitation Database,²⁸ which also includes data from municipalities in 3 of 5 regions (Supplemental Digital Content 1, Table A, available at: https://links.lww.com/JCRP/A673).²⁸

The study involved two populations and follow-up periods (Figure 1). The hospital population included patients ≥18 years who were identified with IHD from April 1, 2019 to March 31, 2022 in the National Patient Register.²⁵ Acute coronary syndrome, unstable angina pectoris, and stable IHD were defined using the codes and classifications as described in the Supplemental Digital Content 1, Table B, available at: https://links.lww.com/JCRP/A673.^25,28 Only patients who were not hospitalized with IHD in 12 months before the index hospitalization and patients who survived for 14 days were included in the hospital population (n = 43 503). These patients were followed from discharge (inpatients) or elective cardiothoracic intervention (outpatients) until 14 days after the index hospitalization regarding CR needs assessment. The CR population included patients ≥18 years who survived for 14 days after the index hospitalization and attended CR in hospital or community health care centers (n = 21 576). These patients were followed from the day of the first CR attendance until completion of the CR pathway (Supplemental Digital Content 1, Table A, available at: https://links.lww.com/JCRP/A673 defines the CR pathway). Patients in the two populations were included multiple times if they were re-enrolled during the study period.

Figure 1.

Flowchart of included patients with IHD in the hospital and the CR population in Denmark, 2019–2022. Abbreviations: CR, cardiac rehabilitation; IHD, ischemic heart disease.

VARIABLES

Socioeconomic Position

Four indicators of socioeconomic position were selected based on prior knowledge of their proposed mechanisms related to cardiac health.^19,31 Educational attainment was included in the primary analyses, while disposable household income, workforce status, and living with another adult (cohabitant status) were used in secondary analyses. The latest updated information on the 4 indicators before patient discharge was obtained from national databases with high validity and coverage.^24,26,27 The highest attained level of education was classified according to the International Standard Classification of Education as follows: low (lower than primary, primary, and lower secondary education), medium (upper secondary and post-secondary nontertiary education), and high (tertiary education).^26,32 The disposable household income was categorized into five groups with an equal number of patients in each group.²⁷ Workforce status, defined by primary income source or occupation,³³ was categorized into employment/education, age-related pension/early retirement, or social benefits (eg, unemployment, sick leave, and social security).^27,33 Cohabitant status specifies whether 2 adults share the same address.²⁴

Endpoints

The 11 CR components defined in Supplemental Digital Content 1, Table A, available at: https://links.lww.com/JCRP/A673 were used to assess the comprehensive clinical CR pathway: no CR needs assessment within 14 days post-discharge; no patient education; no physical exercise training; no physical exercise training within 28 days post-discharge (excluding patient treated with coronary artery bypass grafting); completion of <75% of the planned physical exercise training sessions; no test of CRF conducted at both the start and end of the exercise training program; no depression screening; and no finalizing CR meeting. Dropout was defined by a patient completing none of these: ≥75% of planned exercise training sessions, test of CRF, and attendance to the finalizing CR meeting. Analyzing the possible impact of CR, the endpoints also include no improvement in CRF (increase <10%) and no smoking cessation. Missing values were classified as a nonutilization event, except for improvement in CRF and smoking cessation, where patients with missing values were excluded from the analyses. The information was obtained from the Danish Cardiac Rehabilitation Database²⁸ and the National Patient Registry.²⁵ The clinical CR team registered patient-level data directly into an online system at the time of CR enrollment and at 6 months follow-up in the Danish Cardiac Rehabilitation Database.²⁸ The collected data are linked with nationwide administrative patient registers via the unique personal identification number and approved by the clinical staff.²⁸ The quality of the data is further assessed by annual data audits and by continuous feedback to the clinical staff, allowing ongoing data verification.²⁸

Covariates

Information on age,²⁴ sex,²⁴ country of origin,²⁴ IHD diagnosis,²⁵ cardiothoracic intervention,²⁵ and comorbidities²⁵ was obtained from national databases at the time of hospital discharge, as these factors have been linked with nonutilization of CR.⁶ The number of comorbidities was defined as the count of conditions included in the Charlson Comorbidity Index.³⁴ The conditions were identified by the International Classification of Diseases, 10th revision codes in the National Patient Registry up to 10 years before discharge and up until the index admission for myocardial infarction.³⁴ Information on smoking status (yes/no), consuming ≥180 g of alcohol per week (yes/no), days from discharge to CR uptake, and duration of the CR pathway was attained from the Danish Cardiac Rehabilitation Database.²⁸ Information on the number of persons who died by 280 days of discharge was obtained from the civil registration system.²⁴

STATISTICAL METHODS

Associations between each indicator of socioeconomic position and each CR component were analyzed by crude and multivariable logistic regression adjusting for age (continuous), sex (male/female), country of origin (Danish/Western/not Western), IHD diagnosis (acute coronary syndrome/unstable angina pectoris/stable IHD), cardiothoracic intervention (percutaneous cardiac intervention/coronary artery bypass grafting), and number of comorbidities (0, 1, 2+). Using the Huber–White sandwich estimator, robust standard errors accounted for repeated measurements within individuals, as 3% and 2% of the patients in the hospital and CR population were enrolled more than once. Analyses were performed using complete-case analyses, a significance level of .05, and two-tailed testing in STATA 18.³⁵ The analyses were repeated for the periods with and without the COVID-19 lockdown (March 11, 2020 to January 31, 2022) to examine differences between the periods.

RESULTS

Of the 45 497 patients diagnosed with IHD in the hospital, 43% (n = 19 573) of the patients attended CR. An additional 2018 patients with IHD attended CR without preceding hospital contact for IHD from March 31, 2018 to March 31, 2022 and were included in the CR population (Figure 1). In the hospital population, 18% had higher educational attainment, 48% medium, and 34% lower education, which is largely comparable to the CR population (19%, 51%, and 30%, respectively). Well-known educational differences in the hospital population were largely maintained in the CR population. The group with lower educational attainment had higher proportions of individuals with lower household income, receiving social benefits rather than being employed, and living alone compared with those with higher educational attainment. Differences in demographic and clinical characteristics were also observed, as this group more often was female, treated with coronary artery bypass grafting, and having more than 2 comorbidities. At CR uptake, patients with lower educational attainment were more often smoking (Table 1). During 280 days of follow-up in the hospital population, mortality rates were 4% (n = 280) among patients with higher educational attainment, 5% (n = 931) among those with medium educational attainment, and 7% (n = 1044) among those with lower educational attainment.

Table 1.

Baseline Characteristics of Patients Discharged From the Hospital (N = 41 782) and Taking up Cardiac Rehabilitation in Denmark by Education Status (n = 21 120), 2019–2022^a

	Long Education			Medium Long Education		Short Education
	Hospital Population (n = 7353)	CR Population (n = 3947)	Hospital Population (n = 20 216)		CR Population (n = 10 741)	Hospital Population (n = 14 213)	CR Population (n = 6432)
Age, yr	68 (59, 76)	67 (59, 74)	68 (59, 76)		66 (58, 73)	72 (61, 80)	69 (59, 77)
Sex
Male	4978 (68%)	2891 (73%)	15 024 (74%)		8384 (78%)	8780 (62%)	4317 (67%)
Female	2302 (31%)	1016 (26%)	5046 (25%)		2263 (21%)	5345 (38%)	2068 (32%)
Missing	73 (1%)	40 (1%)	146 (1%)		94 (1%)	88 (1%)	47 (1%)
CVD diagnosis
AMI	3338 (45%)	1805 (46%)	9476 (47%)		5091 (47%)	6924 (49%)	3085 (48%)
Unstable angina	566 (8%)	204 (5%)	1467 (7%)		527 (5%)	928 (7%)	311 (5%)
SIHD	3449 (47%)	1832 (46%)	9273 (46%)		4797 (45%)	6361 (45%)	2823 (44%)
Missing		106 (3%)			326 (3%)		213 (3%)
Intervention
CABG	4338 (59%)	1704 (43%)	12 098 (60%)		4805 (45%)	9235 (65%)	3027 (47%)
PCI	2406 (33%)	1547 (39%)	6641 (33%)		4208 (39%)	4241 (30%)	2485 (39%)
No CABG/PCI	609 (8%)	460 (12%)	1477 (7%)		1094 (10%)	737 (5%)	535 (8%)
Missing		236 (6%)			634 (6%)		385 (6%)
Number of comorbidities
0	3232 (44%)	1893 (48%)	7794 (39%)		4700 (44%)	4416 (31%)	2405 (37%)
1	2256 (31%)	1262 (32%)	6104 (30%)		3429 (32%)	4148 (29%)	2040 (32%)
≥2	1865 (25%)	792 (20%)	6318 (31%)		2612 (24%)	5649 (40%)	1987 (31%)
Smoking statusb
No		3346 (85%)			8328 (78%)		4617 (72%)
Yes		506 (13%)			2173 (20%)		1677 (26%)
Missing		95 (2%)			240 (2%)		138 (2%)
Alcohol per weekb
<180 g pure alcohol		3134 (79%)			8730 (81%)		5312 (83%)
≥180 g pure alcohol		289 (7%)			550 (5%)		250 (4%)
Missing		524 (13%)			1461 (14%)		870 (14%)
Country of origin
Denmark	6475 (88%)	3534 (90%)	18 424 (91%)		9829 (92%)	12 674 (89%)	5733 (89%)
Western countries	349 (5%)	177 (5%)	659 (3%)		354 (3%)	261 (2%)	105 (2%)
Non-Western countries	451(6%)	221 (6%)	990 (5%)		529 (5%)	1219 (9%)	581 (9%)
Missing	78 (1%)	15 (0%)	143 (1%)		29 (0%)	59 (0%)	13 (0%)
Cohabiting
Yes	5045 (69%)	2889 (73%)	13 509 (67%)		7649 (71%)	7856 (55%)	4054 (63%)
No	2230 (30%)	1043 (26%)	6564 (33%)		3063 (29%)	6298 (44%)	2365 (37%)
Missing	78 (1%)	15 (0%)	143 (1%)		29 (0%)	59 (0%)	13 (0%)
Household income
High	3010 (41%)	1774 (45%)	4146 (21%)		2590 (24%)	1241 (9%)	773 (12%)
Medium high	1935 (26%)	1043 (26%)	4533 (22%)		2656 (25%)	1887 (13%)	1046 (16%)
Medium	1149 (16%)	548 (14%)	4382 (22%)		2306 (22%)	2760 (19%)	1295 (20%)
Medium low	577 (8%)	265 (7%)	3799 (19%)		1728 (16%)	3898 (27%)	1604 (25%)
Low	586 (8%)	288 (7%)	3176 (16%)		1418 (13%)	4347 (31%)	1691 (26%)
Missing	96 (1%)	29 (1%)	180 (1%)		43 (0%)	80 (1%)	23 (0%)
Workforce statusc
Employment	2889 (39%)		7113 (35%)			2753 (19%)
Retirement	3840 (52%)		10 699 (53%)			8909 (63%)
Social benefits	586 (8%)		2341 (12%)			2532 (18%)
Missing	38 (1%)		63 (0%)			19 (0%)

Abbreviations: AMI, acute myocardial infarction; CABG, coronary artery bypass grafting; CR, cardiac rehabilitation; CVD, cardiovascular disease; PCI, percutaneous coronary intervention; SIHD, stable ischemic heart disease.

^aData are presented as median (IQR) or n (%).

^bData are not available for the hospital population.

^cWorkforce status is not reported for the CR population to protect personal data.

Only 10 594 (25%) of the discharged patients were assessed for their CR needs within 14 days. Among those who attended, CR was initiated after a median of 25 days (IQR: 14, 43). Patients with lower educational attainment had 8% higher odds of delayed CR needs assessment (adjusted OR = 1.08: 95% CI, 1.01-1.15). Similarly, patients with a lower household income had 18% higher odds (adjusted OR = 1.18: 95% CI, 1.10-1.27), those receiving social benefit had 15% higher odds (adjusted OR = 1.15: 95% CI, 1.07-1.23), and patients living alone had 16% higher odds (adjusted OR = 1.16: 95% CI, 1.11-1.22) of delayed assessment compared with patients with indicators of higher socioeconomic position (Figure 2 and Supplemental Digital Content 1, Table C, available at: https://links.lww.com/JCRP/A673).

Figure 2.

Socioeconomic differences in the timing of cardiac rehabilitation needs assessment and dropout from cardiac rehabilitation in Denmark, 2019–2022. Abbreviation: CR, cardiac rehabilitation. ^aRed dots indicate OR, and horizontal lines represent 95% CI. Estimates are adjusted for age, sex, origin, ischemic heart disease diagnosis, cardiothoracic surgery, and number of comorbidities (0, 1, 2+). Workforce status not adjusted for age. The number of observations varies in the individual analyses because of missing values.

The median duration of the CR pathway, from the day of CR uptake consultation until the finalizing CR meeting, was 126 days (IQR: 91, 173). A trend indicating longer CR pathways was observed among patients with lower educational attainment (Table 2), despite a nonsignificant higher dropout rate among these patients (Figure 2). Utilization of the remaining CR activities varied highly (Figure 3). Screening for depression was the most often utilized CR activity (72%), whereas starting physical exercise training within 28 days was less common (13%). Consistent educational differences were observed across all CR activities except for attending the finalizing CR meeting (Figure 4). This ranged from 31% higher odds of no test of CRF (adjusted OR = 1.31: 95% CI, 1.18-1.45) to 14% higher odds of not starting physical exercise training within 28 days (adjusted OR = 1.14: 95% CI, 1.00-1.31) when comparing patients with lower educational attainment to higher.

Table 2.

Days From Discharge to Cardiac Rehabilitation Uptake Consultation and Duration of Participation in Denmark by Education Status, 2019–2022 (n = 21 120)^a

	Long Education (n = 3947)	Medium Long Education (n = 10 741)	Short Education (n = 6432)
Days to CR uptake, d	26 (14, 43)	25 (14, 43)	25 (14, 44)
Missing data	106 (3%)	233 (2%)	177 (3%)
Duration of CR, d	125 (88, 168)	126 (91, 172)	127 (91, 177)
Missing data	1338 (34%)	3445 (32%)	2214 (34%)

^aData are presented as median (IQR) or n (%).

Abbreviation: CR, cardiac rehabilitation.

Figure 3.

Utilization (crude percentages) of 9 cardiac rehabilitation components among participants in Denmark (n = 21 120), 2019–2022. Abbreviation: CRF, cardiorespiratory fitness. ^an = 21 120 except for the 3 components: exercise ≤28 days (n = 19 031), improve CRF (n = 4877), and smoking cessation (n = 2636).

Figure 4.

Educational differences in the nonutilization of 9 cardiac rehabilitation components in Denmark (n = 21 120), 2019–2022. Red dots indicate OR, and horizontal lines represent 95% CI. Estimates are adjusted for age, sex, origin, ischemic heart disease diagnosis, cardiothoracic surgery, and number of comorbidities (0, 1, 2+). Abbreviation: CRF, cardiorespiratory fitness.

No significant educational differences were observed in the potential impact of CR on CRF or smoking cessation. However, patients with medium educational attainment had borderline significant lower odds of not improving their CRF compared with those with higher educational attainment (adjusted OR = 0.87: 95% CI, 0.74-1.03) (Figure 4 and Supplemental Digital Content 1, Table D, available at: https://links.lww.com/JCRP/A673). The CR pathways for patients with medium educational attainment compared with higher also tended to be more favorable, with higher utilization of physical exercise training within 28 days post-discharge, ≥75% of planned physical exercise training sessions, screening for depression, smoking cessation, attendance at the finalizing CR meeting, and lower dropout rates (Figures 3 and 4, and Supplemental Digital Content 1, Tables C and D, available at: https://links.lww.com/JCRP/A673).

Supplemental analyses demonstrated that fewer patients enrolled in the hospital (≈5%) and the CR (≈12%) populations during the COVID-19 lockdowns. Similar tendencies were observed regarding socioeconomic differences, although some changes in the level of significance were noted. For instance, an overall nonsignificant difference in the odds of no CRF improvement comparing patients with lower and higher educational attainment (adjusted OR = 0.94: 95% CI, 0.78-1.13) became statistically significant during the lockdown (adjusted OR = 0.78: 95% CI, 0.61-1.00).

DISCUSSION

This nationwide follow-up study of 43 503 hospitalized patients with IHD demonstrates that early CR needs assessment is rarely adopted and that the utilization of CR activities varies considerably. Social inequality is present across the CR pathway, disadvantaging persons with indications of lower socioeconomic position, and potentially benefiting those with medium high socioeconomic position when compared with persons with higher socioeconomic position. Addressing social inequalities in early assessment for CR seems crucial for mitigating disparities in the subsequent CR pathways, as early enrollment may enhance CR participation^12,13 and improve cardiovascular outcomes.¹⁴

INTERPRETATION

Consistent with previous research, this study finds a decline in CR uptake during COVID-19; however, contrary to expectations, social inequality does not appear to have increased during the pandemic.³⁶ The demonstrated participation rate of 43% is relatively high compared with studies from other Western countries, which are generally below 37%.^8,37 This could be attributed to several distinctive aspects of the Danish health care system. Universal, tax-financed health care and free access to hospital services and CR likely mitigate financial barriers that may limit participation in other settings.³⁸ Furthermore, systematic referral to CR and early assessment of the need for CR within 14 days post-discharge are endorsed by national clinical guidelines, instructions from the Danish Society of Cardiology, and nationwide monitoring of CR performance in the Danish Cardiac Rehabilitation Database.²⁸ Cardiac rehabilitation is typically provided within short distances, with free transportation available for those unable to travel independently, reducing the potential negative influence of travel time on participation.^6,39 A more recent study period may also have contributed to higher CR participation, as CR participation has been shown to increase over time.⁸

Still, significant socioeconomic differences in early CR needs assessment were demonstrated. Only 24% of the patients with lower educational attainment underwent early assessment. Given that early CR enrollment appears to be associated with improved participation,^12,13 better cardiovascular outcomes,¹⁴ and is acceptable to patients even following sternotomy,^40,41 reducing inequality in early CR needs assessment as a gateway to timely enrollment should be a central priority. Effective interventions for increasing CR adherence in patients with lower socioeconomic position and expectedly timely initiation are financial incentives and early case management, assigning a designated trained individual to assist the patient.^42,43

The substantial need for CR among patients with lower socioeconomic position is underscored by their markedly higher risk profiles at entry to CR compared with those with higher socioeconomic position.²⁰ The core components of CR analyzed in this study target these risk factors, and the results strongly call for action. Proposed mechanisms driving social inequality in CR include an unhealthy lifestyle, health beliefs that conflict with the health care system, travel barriers, and low self-efficacy in making lifestyle changes.³⁹ Pain, comorbidities, and the need to conform to the lifestyle preferences of family and friends may also play a role.^39,44 Interventions to reduce social inequality throughout the CR pathway must address these factors. This study proposes that lower educational attainment (ie, lower than primary, primary, and lower secondary education) constitutes a relevant target threshold for intervention since patients with medium and higher educational attainment generally utilized CR activities more often compared with those with lower educational attainment (Figure 3).

STRENGTHS AND WEAKNESSES

A limitation of the study is its observational design and the risk of confounded results. For example, the considerable proportion of persons with ≥2 comorbidities among patients with lower educational attainment may have amplified the observed associations in the case of inadequate adjustment and residual confounding. Comorbidities are more prevalent among patients with lower socioeconomic positions and may have influenced their ability to attend CR.^39,45 Furthermore, the present findings may have been influenced by unaccounted confounding factors such as sedentary lifestyle³⁹ and logistical barriers to participation.^39,45 Unaccounted confounding could introduce bias in varying directions; for instance, a contradictory relationship between employment status and nonutilization of CR has been proposed.⁶ The strengths of the study include the nationwide design, the identification of patients with IHD and indicators of socioeconomic position from high-quality registers with population coverage, and follow-up across the comprehensive CR pathway, including information from both the hospitals and the community health care centers. The observed CR uptake rate was relatively high,^8,37 despite the potential underestimation due to the inclusion of all hospitalized patients with IHD regardless of their CR eligibility, signifying comprehensive follow-up on CR uptake. Less than 4% of the information on the 4 indicators of socioeconomic position was missing, and high data validity reduces the risk of information bias.^23,24,26,27 Furthermore, the mandatory registration and ongoing verification of information regarding the utilization of CR activities safeguard accurate tracking of the CR pathway and reduce the risk of information and selection bias.²⁸

CONCLUSIONS

This study underscores the need for targeted clinical interventions to mitigate socioeconomic differences in the CR pathway and identifies specific patient characteristics and CR activities as key markers for reducing these inequalities.

ACKNOWLEDGMENTS

We thank the prior CR participants for generously sharing their experiences and insights, which have significantly enhanced the user-perspective interpretation of the study results. Furthermore, we thank the Human First Group, https://www.human-first.org/om-os/english/ , for supporting this research.