NEW YORK (Reuters Health) - The rate of occurrence of peripheral artery disease is greater in blacks than whites in the United States, and various risk factors for heart disease do not completely account for the difference, researchers report.

Peripheral artery disease affects the circulation in the legs, and can lead to pain and difficulty walking. Dr. Joachim H. Ix of the University of California, San Diego and colleagues note that traditional risk markers such as diabetes and hypertension have failed to account for the high rate of peripheral artery disease in African Americans.

To investigate whether other risk factors might shed light on the matter, the researchers studied 104 patients with peripheral artery disease and 164 matched "controls."

Compared to others in the study, African Americans had a threefold higher risk for peripheral artery disease, the team reports in the Journal of the American College of Cardiology. Factoring in traditional risk factors and certain non-traditional risk markers reduced the likelihood to two-fold, according to the article.

The main non-traditional risk factors that made a difference were levels fibrinogen, associated with clotting, and lipoprotein (a), which is involved in plaque build-up in arteries.

Summing up, Ix told Reuters Health, "We observed that the c****ination of traditional risk factors like higher *lo** pressure and diabetes, in conjunction with the new risk factors accounted for approximately 60 percent of the higher prevalence of African-Americans compared to Caucasians. Thus, approximately 40 percent of the higher prevalence remains unexplained in our study."

The investigators say life-style and genes may be the missing link.

SOURCE: Journal of the American College of Cardiology, June 17, 2008.