Being African American can double your risk of developing clogged leg arteries –
a condition called peripheral artery disease (PAD), according to a study in
Circulation: Journal of the American Heart Association.
“Our study found that African-American ethnicity was a strong and independent
risk factor for peripheral arterial disease,” said lead author Michael H.
Criqui, M.D., M.P.H., professor of medicine and professor of family and
preventive medicine at the University of California, San Diego School of
Medicine.
In PAD, arteries outside of the heart and brain – most often the legs –
become clogged by cholesterol-rich plaque. The classic complaint is
intermittent claudication – painful cramping in the hips, thighs or calves that
occurs during exercise and eases a few minutes after stopping. When the leg
blockage is severe, pain is more constant. Severe PAD can also slow the healing
of wounds to the feet and, in severe cases, may lead to amputation.
PAD is a marker for atherosclerosis elsewhere in the body. An estimated
eight million Americans have PAD.
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Criqui suggested that physicians be alert to the possibility of PAD in
African Americans.
“Physicians decide which patients to check carefully for PAD based on their
age and other risk factors,” he said. “This research says that physicians need
to be particularly alert to the possibility of PAD in their African-American
patients. Their independent increased risk is as high as someone in another
ethnic group 10 years older, or someone their own age who smoked a pack of
cigarettes for 20 years.”
Researchers examined 2,343 people, ages 29 to 91, for the presence of PAD.
They compared rates among members of four ethnic groups – 1,401 non-Hispanic
whites, 322 African Americans, 341 Asians and 279 Hispanics. Most were randomly
chosen from current or retired employees of the University of California San Diego and their spouses,
and most participants had health insurance and access to medical care.
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Previous studies of ethnicity and PAD underestimated the occurrence of the
disease by classifying people as unaffected if they currently showed good
circulation but had previously undergone surgery to unblock a clogged artery,
Criqui said.
In this study, researchers used Doppler ultrasound to measure blood pressure
in the leg arteries, and compared blood pressure readings taken in the ankles
with those in the arms (the ankle-brachial index) to look for a deficit in
lower-limb circulation. People were considered to have PAD in any of three
circumstances:
- blood pressure in the ankles was less than 90 percent of the arm
measurements; - blood pressure in the leg arteries was abnormal;
- or they previously had surgery for PAD;
Overall, there were 104 cases of PAD. Men (6.1 percent) were more likely to
be affected than women (3.6 percent). The rates of PAD increased sharply with
age, roughly doubling for each decade from 1.2 percent for those age 50 and
younger to 10.2 percent for those age 70 or older.
In the ethnic group comparisons, researchers found PAD in 7.8 percent of
African Americans, 4.9 percent of non-Hispanic whites, 1.8 percent of Hispanics
and 1.4 percent of Asians.
“We did not have enough Hispanic or Asian participants to definitively
exclude any ethnic differences in PAD, but there did not seem to be a pronounced
difference,” Criqui said.
Several factors significantly raised the risk of PAD in the study — diabetes,
hypertension, cigarette smoking, a ratio of high total cholesterol to low HDL
cholesterol and a history of cardiovascular disease. After controlling for
these factors, African Americans had 2.34 times the risk of non-Hispanic
whites.
To determine whether the higher incidence of PAD in African Americans might
be related to less vigorous treatment of cardiovascular risk factors, the
researchers examined medication records. They found that African Americans with
high blood pressure or high cholesterol were just as likely to be taking
medication for these conditions as participants in other ethnic groups.
“It had been presumed that the excess of PAD in African Americans was due to
a greater proportion of African Americans having diabetes and hypertension,”
Criqui said. “Even though we found a link with those conditions, we were
surprised that they only explained part of the risk. For reasons that are still
unclear, something related to African-American ethnicity raises the risk of
PAD.”
Co-authors are: Veronica Vargas, B.A.; Julie O. Denenberg, M.A.; Elena Ho,
M.P.H.; Matthew Allison, M.D., M.P.H.; Robert D. Langer, M.D., M.P.H.; Anthony
Gamst, Ph.D.; Warner P. Bundens, M.D., M.S.C.; and Arnost Fronek, M.D.,
Ph.D.
The research was supported in part by the National Heart, Lung, and Blood
Institute and the American Heart Association.
Editor’s Note: The American Stroke Association, a division of the
American Heart Association, is launching Power To End Stroke – a movement
to aggressively reach African Americans, who are at highest risk for stroke.
For information about Power To End Stroke, call 1-888-4-STROKE or visit
strokeassociation.org.
Statements and conclusions of study authors that are published in the
American Heart Association scientific journals are solely those of the study
authors and do not necessarily reflect association policy or position. The
American Heart Association makes no representation or warranty as to their
accuracy or reliability.
