Race Difference Confounds Heart Researchers
Studies of drug effectiveness stirs more debate
WEDNESDAY, May 2 (HealthScout) -- While African-Americans are known to be more prone to high blood pressure than whites, a new study finds that blacks also are less likely to respond to one drug used to improve heart function.
However, a second study of another drug, also used to ease strains on the heart, finds no racial differences.
"In the treatment of hypertension [race has] been a factor for a long time and these articles raise that issue and at least highlight awareness about it," says Dr. Milton Packer, a Columbia University cardiologist and co-author of one study, which appears in the May 3 issue of the New England Journal of Medicine.
The first study compared the effectiveness in blacks and whites of the drug enalapril, an angiotensin-converting-enzyme (ACE) inhibitor prescribed to improve heart function. Dr. Derek Exner of the University of Calgary in Canada and his colleagues looked at data from two previous trials with enalapril, covering about 1,200 whites and 800 blacks, who took the drug to both treat and prevent heart failure.
Whites on the drug had a 44 percent lower risk of hospitalization for heart failure, compared with placebo treatment, while blacks who took it saw no significant reduction, the researchers found. And while whites saw marked improvements in blood pressure and heart rate, blacks did not.
Blacks also had about a 25 percent higher death rate (12.2 per 100) than whites (9.7 per 100) from all causes, the study shows, though enalapril didn't appear to reduce mortality in either group.
The second study also looked at black and white heart patients but with a different drug, carvedilol, one of a family of medications known as beta-blockers. These compounds take strain off the heart by easing its workload and cutting down on how much oxygen the organ demands.
A research team led by Dr. Clyde Yancy of the University of Texas Southwestern Medical Center in Dallas analyzed results from a study of carvedilol that included 217 black and 877 non-black men and women.
This time, however, the drug performed equally well in both groups, and researchers could find no racial bias in the progression of heart failure, hospitalizations or deaths from the condition.
Packer says another recent study found that other beta-blockers might not work as well for blacks as they do for whites. However, carvedilol has a slightly different means of action that could explain its better performance in African-American patients, he says.
Dr. Alastair Wood, vice chancellor of Vanderbilt University School of Medicine in Nashville, Tenn., and author of an editorial accompanying the journal article, says, "As physicians, we have a number of choices: Either we give everybody the same dose and assume everybody responds the same way, which we know is not true, or we look for characteristics" that can affect how the drug will perform.
Some of those factors might be genetic, such as the lack or reduced expression of a gene involved in drug metabolism, or they might be cultural, such as the influence of diet. Whatever the case, Wood says drug interaction is not likely to be an "all-or-none" affair; rather "it's going to vary by individual."
However, in a separate editorial, Dr. Robert Schwartz, a member of the journal's staff, writes that "racial profiling" in medicine is "pseudoscience" without biological foundation. "Race is a social construct, not a scientific classification," he writes.
"Sadly, the idea of race remains ingrained in medicine -- yet these vague epithets lack medical relevance," Schwartz writes. "Although social injustice in access to care exists and merits further study, "tax-supported trolling of data bases to find racial distinctions in human biology must end."
Packer disagrees that race is a clinically worthless concept, but he admits it's not a particularly descriptive one.
"The concept of classifying patients by race is an oversimplification, because what race does is simply identify people or groups of patients who have a certain statistical likelihood of certain gene patterns," Packer says.
"But it is much better to identify the gene patterns and patients with those patterns than to identify" groups predisposed to them. "Race is a convenient proxy, but it is probably not an appropriate proxy," he says.
What To Do
Heart failure is one of the nation's leading killers, afflicting roughly 3 percent of African-Americans.
Read other HealthScout articles about drugs for the heart.