There were notable differences and similarities in the treatment and outcome of myocardial infarction according to race and sex from 1994 through 2002. As compared with white men, fewer black men and black women received reperfusion therapy and coronary angiography, whereas black women had the highest adjusted mortality rate among all sex and racial groups. In contrast, differences in treatment and mortality between white women and white men were generally small, as were differences between any of the four racial and sex groups in the use of aspirin and beta-blockers. Racial and sex differences were essentially unchanged between 1994 and 2002.
Management differences were greater when patients were compared according to race within each sex (black men vs. white men and black women vs. white women) than when they were compared according to sex within each race (black men vs. black women or white men vs. white women), suggesting that disparities according to race may be more important than disparities according to sex. Black women had the highest risk of not receiving reperfusion therapy and coronary angiography. Several previous studies also documented less aggressive management of coronary disease in both women5–11
The few studies that examined subgroups classified according to both sex and race also found the lowest rates among black women.13,26,27
Treatment differences according to sex and race persisted without much variation between 1994 and 2002. Although several studies investigated time trends in management of acute myocardial infarction,28–30
none examined such trends with respect to patients’ sex or race. Studies of patients who were referred for cardiovascular evaluation31,32
found little difference in management according to sex, with little variation over time. One study that was based on administrative Medicare databases found smaller differences between blacks and whites in the use of coronary angiography and revascularization procedures in 1997 than in 1986.33
Since results were adjusted only for sex and age, variations over time may reflect variations in the characteristics of patients or in their diagnoses, rather than in patterns of use in health care.
Despite considerable debate, reasons for these differences are largely unknown. Potential explanations are sex and racial differences in eligibility for treatment, clinical contraindications, and confounding by other clinical factors.34
We mostly excluded these possibilities by focusing on ideal candidates and by adjusting for characteristics of patients and hospitals, although some misclassification is possible. It seems unlikely that misclassification affected our conclusions, because such errors should not have occurred differentially according to sex, race, or study year.
The preferences of patients regarding therapy may play some role in the treatment differences that were observed. Data on patients’ preferences in NRMI were limited to reperfusion therapy in the latest years; therefore, we could not account for the preferences of patients in our analysis. However, available data indicated very low rates of refusal (less than 0.5 percent) in all sex and racial subgroups. Incomplete information regarding the time of the onset of symptoms could also contribute to differences in reperfusion therapy. These data were more often missing for white women, black men, and black women than they were for white men. To minimize potential bias, only patients with complete information regarding this factor were considered ideal candidates for reperfusion.
Probably, persistent differences in treatments and procedures according to sex and race reflect some unmeasured characteristic of patients or a health care factor that has not changed over time. There may be differences according to sex and race in the early presentation of myocardial infarction that lead to a delayed diagnosis in black women, white women, and black men. This may affect early treatment in these groups, particularly the use of reperfusion. Similarly, unmeasured health care factors may lead to inequalities in the delivery of care among demographic groups. A recent study found that black patients tend to be treated by primary care physicians with lower qualifications and to have less access to subspecialist care, diagnostic imaging, and nonemergency hospital admissions.35
Although these results cannot be extrapolated to acute inpatient care, provider-level differences according to race may exist during an admission for myocardial infarction — for example, the likelihood or timing of referral to a specialist. Hospital-specific effects may also account for a large portion of racial and ethnic disparities in the time to reperfusion therapy,36
suggesting important unmeasured hospital-level factors — perhaps poorer-quality centers treating a disproportionate number of minority-group patients. This, however, is not consistent with our observation of larger treatment disparities, in comparison with white men, for black women than for black men, two groups who presumably have similar rates of use of hospitals that serve members of racial minorities.
The lack of narrowing in some differences in treatment according to sex and race in recent years is a cause for concern. Differences in treatment paralleled to some extent differences in mortality in our study, since black women were also the group with the highest adjusted in-hospital mortality rate. A full understanding of the reasons underlying such differences requires further study.
Although clinical guidelines for the treatment of acute myocardial infarction changed somewhat during the study period, that change should not affect our results, since we focused on patients who, at each time point, were ideal candidates for each intervention and since the definition was the same for each sex and racial subgroup. We lacked information on whether a history of asthma, chronic obstructive pulmonary disease, dementia, or conduction disorders may have limited the use of beta-blockers or whether a history of hypersensitivity to salicylates or active ulcer disease may have discouraged the use of aspirin. There is no reason to expect that these contraindications differed according to sex or race over time. We also lacked data on socioeconomic factors, such as education and employment status, and were unable to separate the role of sex or race from these factors. Information regarding the time of the onset of symptoms was not available for all patients. The quantity of these missing data increased over time in all sex and racial subgroups with similar trends, making it unlikely that missing values introduced bias. Finally, we did not have access to angiographic data, so we cannot exclude the possibility that observed differences in rates of revascularization after coronary angiography reflected overuse of procedures in white men, rather than underuse in other groups of patients. For this reason, rates of revascularization procedures were considered secondary end points.
Differences in some treatments and procedures, particularly reperfusion therapy and coronary angiography, according to sex and race persist after myocardial infarction, with no substantial changes from 1994 to 2002. Black women, the group with the lowest rate of use of interventions, have higher mortality rates than do other groups. Although the reasons for these differences are unknown, their persistence emphasizes the need for a continued search for explanations so that inequities in clinical care may be eliminated.