Socioeconomic inequalities in access to treatment for coronary heart disease: A systematic review

Highlights

• Low socioeconomic status is associated with lower access to treatment for CHD.

• Inequalities exist more often in countries without universal health coverage.

• Socioeconomic inequalities exist predominantly in access to coronary procedures.

• Inequalities diminish along the pathway from diagnosis to secondary prevention.

Abstract

Strong socioeconomic inequalities exist in cardiovascular mortality and morbidity. The current review aims to synthesize the current evidence on the association between socioeconomic status (SES) and access to treatment of coronary heart disease (CHD). We examined quantitative studies analyzing the relationship between SES and access to CHD treatment that were published between 1996 and 2015. Our data sources included Medline and Web of Science. Our search yielded a total of 2066 records, 57 of which met our inclusion criteria. Low SES was found to be associated with low access to coronary procedures and secondary prevention. Access to coronary procedures, especially coronary angiography, was mainly related to SES to the disadvantage of patients with low SES. However, access to drug treatment and cardiac rehabilitation was only associated with SES in about half of the studies. The association between SES and access to treatment for CHD was stronger when SES was measured based on individual-level compared to area level, and stronger for individuals living in countries without universal health coverage. Socioeconomic inequalities exist in access to CHD treatment, and universal health coverage shows only a minor effect on this relationship. Inequalities diminish along the treatment pathway for CHD from diagnostic procedures to secondary prevention. We therefore conclude that CHD might be underdiagnosed in patients with low SES. Our results indicate that there is an urgent need to improve access to CHD treatment, especially by increasing the supply of diagnostic angiographies, to reduce inequalities across different healthcare systems.

Introduction

Cardiovascular disease morbidity and mortality are strongly associated with socioeconomic status (SES) [1], [2], [3]. Patients with low SES show higher morbidity, which is attributable to the increased prevalence of cardiac risk factors among these patients. Such risk factors include hypertension, cigarette smoking, obesity, and diabetes [4]. Therefore, patients with low SES have a greater need for medical services. SES-related differences in coronary heart disease (CHD) mortality are related not only to cardiac risk factors but also to unequal access to treatment [5], [6]. Guidelines have been developed to standardize treatment and thereby reduce mortality by providing a comprehensive overview of current evidence-based recommendations. CHD treatment includes both non-invasive and invasive cardiac procedures, such as coronary angiography (CAG) and revascularization (percutaneous coronary intervention, PCI; coronary artery bypass grafting, CABG), pharmacological treatment, and rehabilitation. The guidelines state that treatment should be equally provided to all patients according to their health status and needs [7], [8], [9], [10]. In addition, universal healthcare systems provide, at least in theory, access to treatment that is independent of SES [11].

Although most healthcare systems are organized in a fairly equitable manner, international studies have indicated that patients with CHD have unequal access to treatment [5], [12], [13]. However, many of these studies were performed before the implementation of guidelines, in an era when, for example, PCI was not the gold standard for the treatment of acute myocardial infarction (AMI). To the best of our knowledge, only one review has reported on the relationship between socioeconomic inequalities and treatment access among patients with CHD. Quatromoni and Jones [14] focused on studies from the USA and the UK and measured treatment access according to waiting times for and availability of invasive cardiac procedures. They found that patients with low SES waited longer and experienced reduced rates of CAG, PCI and CABG. Additionally, few reviews have analyzed the predictors of access to cardiac rehabilitation (CR) for patients with CHD, and those showed that income and education are associated with referral and participation, to the disadvantage of patients with low SES [15], [16], [17]. Access to and utilization of healthcare cannot be clearly differentiated in the majority of international studies. Access to healthcare is a characteristic predominantly based on care-provider availability and healthcare system design and is determined by supply and demand. In contrast, utilization of healthcare is a characteristic predominantly based on patient preferences and choices [18], [19]. For example, when measuring rates of dispensed drugs using register data, it remains unclear whether patients lacking dispensed drugs received no prescription/had no access to drugs or whether they simply did not utilize their access to drugs by not filling an issued prescription. Therefore, when using the term “access” in this review, we are not indicating whether the barrier is associated with the system or the patient.

The relationship between access to CHD treatment and SES across different countries is unclear, especially since treatment has been standardized through guidelines, and it is unknown at what stage (e.g., diagnosis, revascularization, or secondary prevention) the relationship is most pronounced. Furthermore, it is not known how the relationship between SES and access to treatment differs when using different measures of SES and in the context of different types of healthcare systems. Therefore, the current study aimed to summarize the existing evidence on the relationship between socioeconomic inequality and access to treatment for CHD.