Some black Americans have a gene that protects them from heart disease, researchers said on Thursday.
About a quarter of African-Americans carry the protective gene, and if they are lucky enough to have two copies, one from each parent, their risk of heart disease is 10 times lower that of other blacks.
People with just one copy have five times lower the risk of heart attacks, blocked arteries and other symptoms of heart disease, the team reported in the Journal of Human Genetics.
"What we think we have here is the first confirmed hereditary link to cardiovascular disease among African-Americans and it is a protective one," Diane Becker of Johns Hopkins University in Baltimore said in a statement.
The same gene has been studied in people from Japan, South Korea, Europe and elsewhere but not in black people. In fact, few such genetic studies have been done in blacks at all, the researchers said.
The gene is called CDKN2B, and certain mutations raise the risk of heart disease. For instance, Swedish people with one version of the gene were more likely to have strokes if they also had high blood pressure.
Becker's team studied 548 healthy African-American brothers or sisters of people with documented heart disease. They had their genes sequenced and were followed for 17 years.
The researchers noticed a certain type of mutation called a single nucleotide polymorphism, SNP (pronounced "snip") for short, on a gene that had been linked to heart disease in studies of people in Korea, Italy and elsewhere.
About 25 percent of the volunteers in Becker's study had this protective version of the gene, and 6 percent had two copies.
Becker's team said when genetic tests became more common it might be worth testing blacks for which version of the gene they have, so those without the protective mutation could be more closely monitored for heart disease, the No. 1 killer in the United States and most other developed countries.
It is becoming more common to use ethnic origin to define disease risks.
In 2005, Nitromed Inc. got U.S. Food and Drug Administration approval to market its heart drug BiDil specifically to blacks after it was shown to benefit African-Americans more than whites.
Studies have shown that African-Americans are less likely than whites to be prescribed heart drugs or receive bypass surgery, although blacks have an overall greater risk of heart disease than whites.