A new study published by UT Southwestern researchers may provide insight into ethnic differences in cardiovascular health.

According to the study, African-Americans have more rigid aortas than whites or Hispanics. The aorta is the main artery and supplier of oxygenated blood in the body, and differences in aortic rigidity may explain why African-Americans are at a higher risk of cardiovascular disease. The study was published in the Journal of the American College of Cardiology this month.

Aortic stiffness, which occurs when the artery cannot widen and rebound as the heart pumps, is associated with high blood pressure, target organ damage and a higher overall risk of mortality. The heart has to pump blood more forcefully against a stiffer aorta to maintain the same blood supply, said Wanpen Vongpatanasin, UTSW professor of internal medicine and co-author of the study.

“This may lead to thickening of heart muscle and eventually may lead to damage to the heart muscle,” Vongpatanasin said. “In addition, pulsatile flow caused by increased aortic stiffness may result in damage to the brain and kidneys over time.” 

Studies have already identified African-Americans as being at higher risk of high blood pressure, which is associated with heart attacks and strokes. African-Americans’ mortality rate due to cardiovascular disease is 33 percent higher than that of the general population, according to the American Heart Association, but previous studies had not determined the role the aorta plays in this increased risk. 

UTSW researchers and collaborators used data from the Dallas Heart Study, which looks at social and biological risk factors for cardiovascular health from a multi-ethnic cohort. Two different methods of determining aortic rigidity found that African-Americans have stiffer aortas than Hispanics, who had stiffer aortas than whites. After controlling for weight and other factors, African-Americans and Hispanics had aortas of smaller diameters.

Although researchers are not sure what causes this difference, behavioral and biological variations may be responsible, Vongpatanasin said. 

“Both genetic factors and lifestyle factors, including high sodium or phosphate diet in the processed food, low fruit or vegetable consumption or lack of exercise, may play a role,” Vongpatanasin said.

Another explanation could relate to the content of collagen, a structural protein, in patients’ arteries. Collagen content can differ between ethnicities, according to the study. Differences in how epithelial cells respond to injury may also have a hand in some groups’ increased risk, according to the study. 

Researchers will further investigate differences in cardiovascular health in order to improve screening and treatment, Vongpatanasin said. 

“Additional studies are needed to determine cause of stiffening of aorta in African-Americans and Hispanics to prevent premature heart disease, stroke and kidney damage,” Vongpatanasin said.