Medical researchers said Wednesday they have discovered an abnormal gene that predisposes some people to heart disease, the nation's most common killer, and have developed a test that could someday be used routinely to identify healthy people who are carrying the gene.
Doctors have long suspected that hereditary factors played a role in heart disease, but the new discovery is the first to link a propensity to the disease with a specific, common genetic defect.
About one-third of the people under age 60 who already have coronary artery disease carry the defective gene, the scientists found. By comparison, the defect is present in only about 3% of those with no sign of heart disease.
Although it may be several years before the test is generally available, researchers hope that eventually young people who learn they are carrying the defect will have a powerful motivation to adopt the low-fat, moderate exercise, no-smoking habits that can improve their odds of avoiding heart disease.
The discoveries were reported in Wednesday's issue of the New England Journal of Medicine by a team of researchers from the United States, Canada and Italy.
"We think this test could prove to be a more reliable predictor of the risk of heart disease than anything else we have at the moment," said Ernst J. Schaefer who, along with Jose M. Ordovas, led the scientific team. Both work at the U.S. Agriculture Department's nutrition research center at Tufts University in Boston. Their chief collaborator was Sotirios K. Karathanasis of the Harvard Medical School.
It is not yet clear how the genetic defect works, but the result is to prevent the body from making enough of a normal substance in the blood that removes excess cholesterol deposits from artery walls.
When cholesterol gets too thick inside the arteries supplying the heart muscle, the coronary arteries, the supply of oxygen is pinched off and severe chest pains can result. Also, the narrowed arteries are highly vulnerable to complete blockage if a blood clot suddenly lodges in the opening, causing a heart attack.
The new test for the regulatory defect is done on the genes carried in white blood cells. Schaefer said it would require several years of testing to be certain of its predictive value but that if the early results held up, the test might be commercially available in about five years.