Racial Differences in Long-term Survival among Patients with Coronary Artery Disease

Kevin L. Thomas, MD, FACC; Emily Honeycutt, MBI; Linda K. Shaw, MS; Eric D. Peterson, MD, MPH, FACC

Disclosures

Am Heart J. 2010;160(4):744-751. 

In This Article

Discussion

In this large cohort of patients with CAD, we found that black patients developed CAD at a younger age than whites and had a higher burden of baseline cardiovascular risk factors. Long-term survival rates for blacks were lower than those seen among whites. These differences in survival emerged within the first 3 years of follow-up and persisted over time. Black women had the lowest survival, and white men had the highest. After adjusting for clinical predictors of mortality and initial treatment selection, black race remained an independent predictor of mortality in both women and men.

Early studies suggested that cardiovascular mortality was similar between white and black subjects.[5,11,16–18] More recent studies, however, have indicated that blacks have a higher cardiovascular mortality than whites.[1,2,8,10,19,20] Moreover, blacks have the highest prevalence of risk factors that contribute to the development of significant cardiovascular disease and subsequent poor outcome.[2,3,11,17,20–24] The Multiethnic Atherosclerosis Risk in Communities (MESA) study assessed risk factors in the development of coronary heart disease and cardiovascular-related mortality in 14,062 patients (3,694 black, 10,368 white) from 1987 to 1997. Blacks had more risk factors for CAD and higher cardiovascular death rates than whites.[20] Hypertension was a strong predictor of developing coronary heart disease among all subjects; however, diabetes mellitus was less predictive in blacks than in whites. Although the MESA investigators did document a higher risk profile in blacks versus whites, they did not examine long-term outcomes for blacks and whites with cardiovascular disease.

The higher prevalence of CAD in black women compared with white women seen in our analysis was striking and has been seen in other reports.[25] The reasons for this finding are not readily apparent but may be a reflection of differential risk factors present among women from these racial subgroups. Further research is required to decipher the reasons for this finding.

Our study significantly extends the findings of prior studies by examining risk factor profiles and long-term outcomes among a contemporary cohort of blacks and whites with CAD. We confirmed that black subjects at baseline carried a higher burden of cardiovascular risk factors and ultimately had a higher mortality rate. The significantly higher prevalence of risk factors among blacks in our cohort has been noted in other published reports.[5,20,22–24,26]Differences in the prevalence of risk factors did not fully explain racial differences in the long-term survival of patients with CAD in our population.

Predictors of mortality were largely similar among black and white patients in our analysis. Adjusting for other predictors, black race remained an independent predictor of increased mortality. These findings suggest that additional factors are contributing to long-term survival differences.

Disparate use of revascularization therapy remains a potential cause for differential survival by race. Specifically, we and several others have previously found significant racial differences in surgical revascularization among patients with CAD that contributed to survival differences.[8,27,28] Although blacks were less likely to receive coronary revascularization, this factor alone did not fully explain survival differences. Specifically, stratified analyses demonstrated that blacks had slightly lower survival regardless of initial therapeutic option selected. Racial differences in medical adherence and environmental barriers to a healthy lifestyle (diet and exercise) may represent alternative explanations to disparate outcomes. Other potential explanations for long-term racial differences in survival may include variations in genetic polymorphisms and the degree to which these coupled with environmental exposures may predispose blacks to sudden cardiac death.[3,29–31]

This analysis has several limitations. Despite the size and long-term longitudinal follow-up of our population, the outcome represents the practice patterns and individual patient experiences of a single institution and may not be applicable to the general population. Our cohort of patients includes only those individuals who received diagnostic coronary angiography and thus does not reflect outcomes in those individuals who have not undergone angiography. Traditionally, blacks have been less likely to undergo catheterization; it is unclear how this may have affected our outcomes. The effect of race on cardiovascular outcomes is often intertwined with socioeconomic status. In fact, race may be a proxy for other closely aligned socioeconomic factors including insurance status, education, marital status, and income level, all of which may impact long-term outcomes. In some instances, the determination of race by our administration staff was by observation. Self designation is the preferred reporting of race, and this may have impacted our findings. Despite including median household income and domicile values in our analysis as markers of socioeconomic position, there may have been other socioeconomic variables not included in our data analysis that may have contributed to the racially divergent survival. Furthermore, measures of physical inactivity and stress are important determinants of mortality risk in patients with ischemic heart disease.[32] These metrics were not readily available from our database and may have affected our findings. Medication data were not available and not included in our analysis. Differential use of secondary prevention interventions including medical therapies and lifestyle modifications may also explain remaining racial differences in survival. In 2 non–ST segment elevation MI populations, Sabatine et al[33] and Sonel et al[34] have both reported that nonwhite patients were less likely to be on evidence-based cardiac medications at discharge or 6 months postdischarge. Newby et al[35] reported that long-term adherence to evidence-based secondary prevention medications in patients with CAD from the same database (DDCD) used in this analysis differed by race, with white patients more likely to remain compliant. Moreover, patients who remained adherent to many of the therapies had lower adjusted mortality. Finally, our analysis did not adjust for other downstream factors such as differential access to providers and invasive procedures by race over time that may have impacted our findings.

Cardiovascular disease remains the leading cause of death in the United States for all people. Despite agendas aimed at eliminating or decreasing racial disparities, blacks develop CAD at a disproportionally young age and continue to be plagued by worse long-term outcomes. We demonstrate notable differences in mortality by race. Both black woman and men had higher mortality rates than their white counterparts. Our analysis suggests that survival differences may not fully be explained by the increased prevalence of traditional risk factors among black patients or by racial differences in predictors of increased mortality. These results emphasize the need for ongoing national efforts to reduce disparities in cardiovascular prevention and treatment as well as the need for continued monitoring of morbidity and mortality by race/ethnicity to assess the success of these public health efforts to eliminate racial disparities in health outcomes.

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