Question:
What causes poor circulation in people with diabetes? Is it the blood somehow thickened from glucose, or is it because of a higher incidence of atherosclerosis?

Answer:
Poor circulation is one of the most dangerous consequences of diabetes. People with type 2 diabetes have two to four times the risk of dying from heart disease or having a stroke compared to non-diabetics. More than half of the amputations done in the United States are a consequence of diabetes, and usually the need for an amputation occurs because of damage to the peripheral arteries (arteries to the legs). Poor circulation from artery damage also causes open skin sores and infections for people with diabetes.

Why does diabetes lead to artery damage? Part of the answer is that diabetes usually occurs in the company of other diseases that place the heart and arteries at risk. People with diabetes are more likely than other people to develop high blood pressure, obesity and high cholesterol.

When several heart- or artery-health risks occur together in one person, they present a powerful health threat and are known as the metabolic syndrome.

High levels of glucose (blood sugar) also contribute to artery damage for people with diabetes. This was confirmed by long-term health results for people who participated in the Diabetes Control and Complications Trial (DCCT). After nearly 1,200 patients participated in this trial for an average of more than six continuous years, experts followed the progress of these patients and monitored their health.

The trial had assigned some patients to keep strict glucose goals in mind, advising them to take three or four insulin injections daily. These patients had a higher average A1C (a measure of glucose control) during treatment compared with the other half of the patients in the study, most of whom used one or two daily injections. In the 11 years since the study was discontinued, the “tight control” group and the “loose control” group drifted back together in terms of their sugar control, so that they returned to having essentially the same glucose average from one group to the other. Despite this, the group that had the long stretch of “tight control” has much healthier arteries. Over an average of about 17 years of monitoring, this group has had a 57 percent lower rate of heart attack, stroke, and death from heart disease. In other words, for every three events that have been experienced within the “tight control” group, the “loose control” group has had seven events.

Experts don’t know why high glucose levels contribute to artery damage.

If you are aggressive in treating each risk factor from the metabolic syndrome and if you keep your blood sugar tightly controlled, you can greatly reduce your risk of heart attack and other problems caused by artery injury.

Mary Pickett, M.D., is a lecturer for Harvard Medical School and an assistant professor of medicine at Oregon Health & Science University in Portland, OR. At OHSU, she practices general internal medicine and teaches medical residents and students.