Breaking Health News, November 2, 2005

African Americans at Higher Risk for Leg Artery Disease

Being African American can double the risk of developing clogged leg arteries, according to a study in Circulation: Journal of the American Heart Association.

The condition is referred to as peripheral artery disease (PAD), and can cause problems such as "intermittent claudication."

“Our study found that African-American ethnicity was a strong and independent risk factor for peripheral arterial disease,” says lead author Dr. Michael H. Criqui, a professor of medicine at the University of California, San Diego School of Medicine.

Pain Is the Most Common Problem

In PAD, arteries outside of the heart and brain, most often the legs, become clogged by cholesterol-rich plaque.

The classic complaint is 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 8 million Americans have PAD.

Dr. Criqui suggests 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 notes. “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,” explains Dr. Criqui.

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 Caucasian, 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.

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, says Dr. Criqui.

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.

Participants 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 ages 50 and younger to 10.2 percent for those ages 70 or older.

In the ethnic group comparisons, researchers found PAD in 7.8 percent of African Americans, 4.9 percent of non-Hispanic Caucasians, 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,” remarks Dr. Criqui.

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 Caucasians.

All Risk Factors Considered

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,” Dr. Criqui says.

“Even though we found a link with those conditions, we were surprised that they only explained part of the risk," he notes. "For reasons that are still unclear, something related to African-American ethnicity raises the risk of PAD.”

Always consult your physician for more information.

Online Resources

(These links are provided for the education and convenience of our Neighbors. AAMC is not responsible for the content of Internet sites.)

American Heart Association

Centers for Disease Control and Prevention (CDC)

Circulation

National Heart, Lung, and Blood Institute

National Institutes of Health (NIH)

National Women's Health Information Center

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Claudication: Clogged Artery Symptoms

Claudication refers to limping because of pain in the thigh, calf, and/or buttocks that occurs when walking.

Claudication may be a symptom of peripheral arterial disease (PAD).

PAD is caused by a narrowing or blockage of arteries in the legs and/or aorta (the largest artery in the body and the primary blood vessel leading from the heart to the body), which may cause decreased blood flow to the muscles of the calf, thigh, or buttocks.

This decreased blood flow may cause claudication. The pain associated with claudication occurs with walking but disappears at rest.

Claudication may be a symptom of underlying systemic artery disease and is seen more often in persons who have blockages in other arteries, including the heart and brain.

Because claudication is associated with an increased risk for heart attack or stroke, its presence signals the need for assessment and possible treatment.

About 9 million Americans, about 12 percent of the population, experience occasional claudication.

Of those who are age 70 or older, about 20 percent are affected. About 25 percent of persons who have hardening of the arteries (arteriosclerosis) in the legs experience claudication.

Claudication generally occurs when walking the same distance.

With progressive vessel disease, the initial claudication distance (that distance at which a person first experiences pain when walking) may decrease or the person may no longer be able to walk.

Blockage of an artery in the legs may cause intermittent claudication.

Atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery) is the most common cause of blockage of arteries.

Blockages in the leg are most common in the thigh and behind the knee but may also occur at other sites in the body including the aorta, groin, or abdomen. A person may have more than one blockage.

As stated above, atherosclerosis is the most common cause of arterial blockage which can cause claudication. Risk factors for claudication are the same as those for atherosclerosis, and may include:

• smoking
• diabetes
• overweight or obesity
• sedentary lifestyle
• high cholesterol
• high blood pressure
• family history of atherosclerosis or claudication
• older age (55 for men, 60 for women)

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases have different risk factors.

Although these risk factors increase a person's risk, they do not necessarily cause the disease.

Claudication itself is a symptom of a narrowing or blockage of an artery.

Pain, a burning feeling, or a tired sensation in the legs and buttocks while walking are symptoms of claudication.

In some cases, the sound of blood moving through a blockage (a whooshing sound called a bruit), can be heard through a stethoscope.

The skin of the foot or leg may become shiny, hairless, and/or mottled (blotchy) in appearance, or may ulcerate.

The affected leg may become pale when elevated and reddened (rubor) when lowered.

Additional symptoms that may be present in persons with claudication include cold feet, impotence in men, and leg pain that occurs at night when in bed.

Pain that occurs at rest may be a sign of increasing severity of arterial disease in the leg(s).

The symptoms related to claudication may resemble other medical conditions or problems.

Always consult your physician for a diagnosis.