FRIDAY, Feb. 24, 2006 (HealthDay News) -- Some rare variant forms of genes that control blood clotting can increase the risk of heart disease, a British study finds.
The genes are not common enough and the risk they pose is not great enough to warrant screening for them now, said Dr. John Danesh, a professor of epidemiology and medicine at the University of Oxford, and lead author of a report in the Feb. 25 issue of The Lancet.
"But it is helpful to identify genetic variants that may be associated with increased risk," Danesh said. "This helps increase our understanding of the biological pathways that lead to heart disease. These findings could have implications for designing new therapies that target blood clotting pathways to help prevent heart disease."
There has been a back-and-forth controversy about the possible role of such genes in heart disease, Danesh said. "The whole purpose of this exercise was to try to pool the studies that have been reported and produced conflicting results, and clarify the evidence by pooling the data," he said.
Danesh and his colleges analyzed results of 191 studies that included 66,155 people with heart disease and 91,307 people with no heart trouble, looking for the incidence of seven variants of clotting genes that have been associated with increased risk in some studies. Most of the studies were done in Europe.
The analysis showed no significant association with increased risk for five of the genes. But there was a moderately increased risk for one variant of a gene for plasma protein V and one for the protein prothrombin. Both genetic variants increase the body's production of thrombin, an enzyme that encourages formation of blood clots.
The increased risk is not great, Danesh said. Persons who carry the variant genes have a 15 percent to 20 percent higher risk of developing heart disease than those who do not, the analysis showed. And the genetic variants aren't common, with about 3 percent of whites carrying the protein V version and 1 percent carrying the prothrombin version.
"They are not common enough or associated with enough risk to warrant screening for them," Danesh said. "In the future, if a number of weakly acting gene variants are identified, that might warrant screening. At the moment, the question is hypothetical."
The role of heredity in heart disease is discussed by the American Heart Association.