COLUMBIA, S.C. - African-American women have higher levels of an obscure cholesterol molecule that worsens the risk of coronary artery disease, the nation's leading killer, a new study shows.
Concentrations of the lipoprotein(a) molecule are significantly elevated in African-American women compared with American Indian and Caucasian women, the five-year University of South Carolina study found. Scientists blame genetics.
Making bad news worse, exercise does not noticeably reverse these levels, unlike with other "bad" cholesterol, according to the study, which appears in the current issue of the journal Vascular Medicine.
"We had hoped to find that people who are physically active will have lower levels of this lipoprotein(a). It had little impact," said USC exercise physiologist Larry Durstine, one of the study's eight authors.
That's not a free pass to avoid physical activity, said lead author Katrina Drowatzky, a USC doctoral student.
Lack of exercise and obesity are other risk factors for coronary artery disease, as are smoking, diabetes and hypertension.
Scientists believe that lipoprotein(a) causes cholesterol to build up on artery walls, making arteries narrower and stiffer. Heart attack and stroke are then more likely.
Women at high risk for having elevated lipoprotein(a) concentrations - such as those whose father or mother died young of a heart attack - should consider getting a specific blood test that measures lipoprotein(a) levels.
Standard cholesterol tests don't show this information, said Durstine, a researcher at USC's Norman J. Arnold School of Public Health.
Most people have never heard of lipoprotein(a) but are familiar with HDL cholesterol, known as "good" cholesterol, and LDL cholesterol, the "bad" type. Increasing physical activity can reduce LDL cholesterol in the bloodstream.
Lipoprotein(a) levels can be controlled with medication and can be eased by eating niacin-rich foods such as broccoli, Durstine said.
The new research analyzed data culled from another USC study, the Cross-Cultural Activity Participation Study. It includes 140 women.
African-Americans and Caucasians in South Carolina, and American Indians in New Mexico, kept detailed records of their physical activity, took a treadmill test, gave their health histories, and had blood tests to determine total cholesterol and lipoprotein(a) levels.