Gene Combo Raises Blacks’ Heart Disease Risk, Study Says
A genetic abnormality rarely found in whites dramatically increases the risk of congestive heart failure in blacks and might help explain why they are more likely than whites to get the disease, researchers said in a study published today.
The genetic combination plays a role in a quarter of the cases of congestive heart failure diagnosed each year among blacks, said Dr. Stephen B. Liggett of the University of Cincinnati College of Medicine, who was a leader of the study.
The study found that a pair of genes that does nothing bad by itself can double the risk created by a second pair, generating a tenfold risk for heart failure in black people who have both.
About 5% of U.S. blacks have that combination, Liggett said.
The study was published in today’s New England Journal of Medicine.
In an accompanying editorial, Dr. Roger J. Hajjar of Massachusetts General Hospital called the study provocative but said the researchers had not proved cause and effect.
Doctors have long known that blacks are more likely than whites to suffer from heart diseases and certain other illnesses, and are more likely to die because of them. Some researchers have suggested that blacks receive inferior care, perhaps because of unconscious prejudice among doctors.
In fact, an analysis of 81 studies, released Wednesday as part of a campaign by major health foundations to close the racial health gap, found that the evidence that minorities receive inferior cardiac care is compelling.
Liggett’s study, however, is part of growing research indicating that at least part the racial gap can be explained by genetics.
Discrimination, lack of access to care and other societal inequities are indeed a problem--but might not be the main reason for the gap, said Dr. Clyde W. Yancy of the University of Texas-Southwestern Medical Center in Dallas.
“When you control for those variables, there is still more heart disease in African Americans. Particularly this disease called heart failure,” he said.
Yancy said the next step is to find what other genes are involved and how they affect patients’ response to various drugs.
Nearly 4.8 million Americans have congestive heart failure. It affects about 3.5% of all black men, 3.1% of black women, 2.3% of white men and 1.5% of white women, according to the American Heart Assn.
That would mean about 733,500 blacks have the disease. It shows up earlier and is more likely to have serious complications in blacks than in whites. Also, blacks do not gain as much benefit from or need higher doses of two groups of medicines for heart disease.
There is no one explanation for those differences. What patients do and where they live also can increase the risk. High blood pressure, diabetes, high cholesterol, smoking and obesity all make heart disease more likely.
That means people who have both gene pairs should do everything they can to eliminate the risks they can control, Liggett said.
One of the gene pairs in question increases production of a chemical that increases blood pressure, heart rate and the heart’s contraction and relaxation. The other gene pair makes heart cells that take up the chemical, norepinephrine, more sensitive to it.
Since the pair producing excess norepinephrine is 10 times as common among blacks as among whites, the combination is also far more common among blacks.
In the study, two of the 84 healthy blacks had the combination, compared with 15 of 78 blacks with heart failure. Two out of 105 healthy whites and three of 81 with heart failure had the gene combination.
Even though it was a rare combination in whites, the fact that it was present is important, Yancy said. He said that indicates that the risk might be in genetics, not race.
