Millions of Americans, including about 5 percent of people older than 50, lose their ability to walk long distances and experience pain or numbness because of peripheral arterial disease (PAD). PAD occurs when the arteries in your limbs (usually the lower legs) are clogged and circulation slows to those areas. Doctors have sometimes been reluctant to treat PAD because the medical literature said that it did not get worse or even improved with time. However, doctors from Northwestern University reasoned that the disease may not improve but that people may adjust their life to lessen pain. They used an objective test to measure the progression of the disease.

What the doctors wanted to know: Does peripheral arterial disease get worse over time?

What they did: The researchers examined about 400 people with PAD and 250 people without, all over age 55 and living near Chicago. At the patients' first visit, they measured the ratio of blood pressure at their ankles to blood pressure in their upper arms, a common measure of PAD. They also gave the participants a questionnaire asking them about pain when walking and resting. Finally, they measured the participants' motor abilities through tests of walking speed as well as endurance and balance. After the initial visit, participants returned one to two years later when the motor abilities tests were done again.

What they found: The motor abilities of people with PAD declined faster over two years than they did in people who did not have PAD. Participants with particularly bad PAD were much less likely to be able to walk for 6 minutes on a treadmill than people without PAD. Even people with PAD who had no symptoms in the initial test did worse after two years on the walking test than people without the disease.

What it means to you: The authors write that their findings "challenge standard thinking" of physicians about the progression of peripheral arterial disease. Most physicians don't think the condition worsens over time, so they're inclined not to treat it. However, this study suggests that PAD should be actively dealt with and not left to get better on its own.

Caveats: In the follow-up evaluation, the authors assumed that PAD was responsible for the loss of motor abilities, but they did not do tests to prove it conclusively. Other diseases, accidents, or conditions could have made some of the participants unable to complete some of the tests in the follow-up. In addition, the researchers assumed that if patients with PAD had leg pain, it was because of the PAD, but it may come from other conditions as well, which the researchers did not measure.

Find out more: The National Institutes of Health has a good website with a description of PAD.

For more about the test to determine PAD, which measures the blood pressure ratio between the ankle and upper arm and is called the ABI index, check out the explanation on the PeaceHealth site, the website for a group of hospitals in the Pacific Northwest.

Read the article: McDermott, Mary McGrae et al. "Functional Decline In Peripheral Arterial Disease: Associations With the Ankle Brachial Index and Leg Symptoms." Journal of the American Medical Association. July 28,2004, Vol. 292, No. 4, pp. 453–461.

Abstract online: http://jama.ama-assn.org