Blacks and whites have similar amounts of coronary calcium deposits, which are a sign of atherosclerotic plaques

In contrast to earlier studies that indicated African-Americans tend to have lower amounts of atherosclerosis than whites, despite having higher cardiovascular death rates, heart scans in a large, representative population indicate that blacks and whites have similar amounts of coronary calcium deposits, which are a sign of atherosclerotic plaques, according to a new study in the Sept. 1, 2004 issue of the Journal of the American College of Cardiology.

“What we found was that blacks have as much coronary calcium as whites and among women there was a trend towards more. That indicates that blacks don’t have less atherosclerosis. There are other papers that went in the other direction, but we think the size of the sample in this study and the fact that it was a random population provides pretty strong evidence that there is as much atherosclerosis,” said Scott M. Grundy, M.D., Ph.D. at the University of Texas Southwestern Medical Center in Dallas.

The researchers, including lead author Tulika Jain, M.D., measured coronary calcium with electron beam computed tomography (EBCT) scans in 1,289 men and women. The participants were part of the Dallas Heart Study, which is a multiethnic, probability-based sample of the Dallas county population in which blacks were systematically over-sampled so the final group was 50 percent black.

Dr. Grundy said although this study indicates blacks and whites have similar rates of atherosclerosis, the study found other differences in cardiovascular risk factors.

“We also found that blacks have a different pattern of risk factors for atherosclerosis and heart disease than whites do. They had more high blood pressure and more diabetes, and the black men were more likely to smoke. The whites had worse lipids. So probably on the whole, the things that cause atherosclerosis were different, but they ended up with the same amount of atherosclerosis,” Dr. Grundy said.

He noted that since high blood pressure, diabetes and smoking can lead to health problems beyond just atherosclerosis, the different patterns of risk factors seen in this study may offer some potential explanations for the higher cardiovascular death rates seen among African-Americans. He said future studies should investigate how different patterns of risk factors may lead to different ultimate outcomes, including death rates.

Dr. Grundy said this study used a larger and more representative sample of people than previously published research, though there can always be questions about whether the study participants truly represent the community as a whole. He pointed out that the participants in this study were generally younger than those in other studies, which may indicate changing patterns of risk factors from one generation to the next. He also noted that coronary calcium scan results may not be a perfect indicator of the extent of atherosclerosis, but EBCT is the best noninvasive screening tool available.

Robert C. Detrano, M.D., Ph.D., F.A.C.C. at the Harbor-UCLA Medical Center in Torrance, Calif., who was not connected with this study, said researchers need to figure out why these results are different from those of other studies.

“This report from the Dallas Heart Study presents evidence that conflicts with that of other large multi-center studies such as the CARDIA study and from other single center studies like the Army PACC study, the South Bay Heart Watch study and the Women's Health Initiative study. The Dallas study finds little difference in the prevalence or amount of coronary calcium in African-American and Caucasian adults. The other studies find that African-Americans have less calcification than Caucasians. This important discrepant finding needs to be placed into the context of the bulk of the literature on this subject,” Dr. Detrano said.

Paolo Raggi, M.D., F.A.C.C. at the Tulane University School of Medicine in New Orleans, who also was not part of this research team, said this study provides an important piece of information. He said earlier studies reporting that African-Americans had less atherosclerosis, despite suffering higher rates of heart disease and death than whites, just didn’t seem to make sense.

“Nonetheless, it remains to be explained why blacks have a greater cardiovascular disease burden in the presence of the same atherosclerosis burden. To me this is another lesson in ‘humility’ as I teach my trainees all the time: ‘There is more that we do not know rather than what we do know about atherosclerosis and cardiovascular disease,’” Dr Raggi said.

The American College of Cardiology, a 31,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.