Does Race Affect Outcomes in Diabetes and CAD?
Beohar N, Sansing VV, Davis AM, et al; BARI 2D Study Group
Am J Cardiol. 2013;112:1298-1305
The BARI 2D clinical trial compared treatment strategies for patients with both type 2 diabetes mellitus and stable coronary heart disease in the context of intensive risk factor control. The current study evaluated the impact of race or ethnicity on long-term risk factor control and cardiovascular outcomes among white, black, and Hispanic participants in BARI 2D in the United States and Canada.
All patients received intensive therapy to achieve risk factor goals for A1c, low-density lipoprotein cholesterol, and blood pressure. For the present analysis, however, the investigators used threshold levels to define good control (all 3 goals met), moderate control (2 goals met), or poor control (0 or 1 goal met).
Participants were assessed each year over 5 years of follow-up. The outcomes of interest were 5-year rates of mortality and a composite of death, myocardial infarction, or stroke.
In this report, 1189 white, 439 black, and 212 Hispanic persons with several important differences in risk factors at baseline were analyzed. At study entry, 35% of white patients, 24% of black patients, and 30% of Hispanic patients were in good control of risk factors. During the trial follow-up period, good control was achieved by 60% of white, 39% of black, and 43% of Hispanic patients; moderate control was achieved by 30%, 37%, and 34%, respectively.
Among the patients with moderate or poor control at study entry, attaining better risk-factor control during the trial was associated with higher 5-year survival in all 3 ethnic groups. Hazard ratios for mortality and the composite outcome by race were not statistically significant, with or without adjustment for baseline risk factors, and the estimates did not change substantially after adjustment for follow-up risk factor control.
Despite known disparities in mortality and heart disease, this report from BARI 2D found no statistically significant difference in such outcomes by race, perhaps because all patients received intensive risk factor therapy. This finding suggests that disparities in outcomes may be uniformly mitigated by equality of therapy. However, it is also important to note that disparities in postintervention risk factor control persisted, with more white patients achieving control of all 3 risk factors than black or Hispanic patients, even though therapies were equivalent.
A simple explanation is that more white patients were in good control at baseline, but there is a more complex explanation worth considering. The Diabetes Prevention Program reported that among study subjects, all of whom had impaired glucose tolerance, A1c was intrinsically higher among black persons than among white and Hispanic persons, after adjustment for factors that were likely to contribute to glycemia. Thus, differences in A1c might not reflect disparities, and it is possible that A1c-based treatment goals for black patients need not be as stringent as for white patients.
In any case, the relative importance of A1c for reducing cardiovascular risk is open to question. Indeed, some studies suggest that the relationship between A1c and cardiovascular disease is U-shaped -- yet another argument for a patient-centered approach to therapy.
Abstract
Race/Ethnic Disparities in Risk Factor Control and Survival in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) Trial
Beohar N, Sansing VV, Davis AM, et al; BARI 2D Study Group
Am J Cardiol. 2013;112:1298-1305
Study Summary
The BARI 2D clinical trial compared treatment strategies for patients with both type 2 diabetes mellitus and stable coronary heart disease in the context of intensive risk factor control. The current study evaluated the impact of race or ethnicity on long-term risk factor control and cardiovascular outcomes among white, black, and Hispanic participants in BARI 2D in the United States and Canada.
All patients received intensive therapy to achieve risk factor goals for A1c, low-density lipoprotein cholesterol, and blood pressure. For the present analysis, however, the investigators used threshold levels to define good control (all 3 goals met), moderate control (2 goals met), or poor control (0 or 1 goal met).
Participants were assessed each year over 5 years of follow-up. The outcomes of interest were 5-year rates of mortality and a composite of death, myocardial infarction, or stroke.
In this report, 1189 white, 439 black, and 212 Hispanic persons with several important differences in risk factors at baseline were analyzed. At study entry, 35% of white patients, 24% of black patients, and 30% of Hispanic patients were in good control of risk factors. During the trial follow-up period, good control was achieved by 60% of white, 39% of black, and 43% of Hispanic patients; moderate control was achieved by 30%, 37%, and 34%, respectively.
Among the patients with moderate or poor control at study entry, attaining better risk-factor control during the trial was associated with higher 5-year survival in all 3 ethnic groups. Hazard ratios for mortality and the composite outcome by race were not statistically significant, with or without adjustment for baseline risk factors, and the estimates did not change substantially after adjustment for follow-up risk factor control.
Viewpoint
Despite known disparities in mortality and heart disease, this report from BARI 2D found no statistically significant difference in such outcomes by race, perhaps because all patients received intensive risk factor therapy. This finding suggests that disparities in outcomes may be uniformly mitigated by equality of therapy. However, it is also important to note that disparities in postintervention risk factor control persisted, with more white patients achieving control of all 3 risk factors than black or Hispanic patients, even though therapies were equivalent.
A simple explanation is that more white patients were in good control at baseline, but there is a more complex explanation worth considering. The Diabetes Prevention Program reported that among study subjects, all of whom had impaired glucose tolerance, A1c was intrinsically higher among black persons than among white and Hispanic persons, after adjustment for factors that were likely to contribute to glycemia. Thus, differences in A1c might not reflect disparities, and it is possible that A1c-based treatment goals for black patients need not be as stringent as for white patients.
In any case, the relative importance of A1c for reducing cardiovascular risk is open to question. Indeed, some studies suggest that the relationship between A1c and cardiovascular disease is U-shaped -- yet another argument for a patient-centered approach to therapy.
Abstract
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