Heart Threats May Lead to Nerve Damage in Diabetics

High blood pressure, cholesterol, obesity increase risk of neuropathy, study says

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HealthDay Reporter

WEDNESDAY, Jan. 26, 2005 (HealthDayNews) -- The same factors that increase the risk of heart disease and stroke -- obesity, smoking, high blood pressure and high cholesterol -- also are associated with diabetic neuropathy, the progressive nerve damage seen in people with diabetes, a European study finds.

The prevention of nerve damage among diabetics has traditionally focused on controlling blood sugar levels. But, "the incidence of neuropathy is associated with potentially modifiable cardiovascular risk factors, including a raised triglyceride [blood fat] level, body mass index, smoking and hypertension," the researchers stated.

Their findings appear in the Jan. 27 issue of the New England Journal of Medicine.

The report comes from the European Diabetes Prospective Complications Study Group, which followed 1,172 people with type 1 diabetes. That's the form of the disease, usually diagnosed early in life, in which the body is incapable of producing the hormone insulin needed to metabolize blood sugar.

In the more than seven years of the study, 276 of the patients developed one form or another of neuropathy, a progressive loss of nerve function that can cause a variety of problems affecting the arms and legs, bowel and bladder activity, and other body functions.

As many other studies have shown, the incidence of neuropathy increased with time and with high blood levels of sugar. But the presence of cardiovascular risk factors was directly related to the development of neuropathy, the researchers reported.

The closest association was with high blood pressure, which increased the risk of neuropathy by more than 50 percent, the study said. It noted that aggressive treatment of high blood pressure is standard clinical practice to prevent kidney damage and eye damage in diabetes, and recommended a controlled trial to show that the same treatment can help prevent neuropathy.

The report provides "more scientific support for why we are doing what we are doing," said Dr. Robert A. Rizza, a professor of medicine at the Mayo Clinic School of Medicine, and a spokesman for the American Diabetes Association.

"The paper adds further strength to the knowledge that keeping blood glucose levels low reduces the chance of having neuropathy," Rizza said. "It also shows that keeping these other risk factors under control also improves nerve function."

Thanks to smaller past studies, doctors who manage patients with diabetes "have known all along that it is important to manage vascular [blood vessel] problems as well as blood glucose," he said. "This is a much larger and more definitive study showing that attention to cardiovascular risk factors protects nerves and arteries, as well as eyes."

Dr. Jayant Dey, an endocrinologist at the Ochsner Clinic Foundation in New Orleans, said, "When we are aggressively treating risk factors such as triglycerides, weight and smoking, we are targeting a reduction in heart attack and stroke. We did not think that it would have any impact on neuropathy, which was believed to be related only to blood sugar control."

The new study takes a step toward changing that attitude, Dey said. But more steps are needed, he said, because the study "did not prove that controlling these risk factors reduced the incidence of neuropathy. What is needed is a treatment study. This was not a treatment study, but that seems to be where we are heading for."

Dey said the findings also apply to type 2 diabetes, which is far more common than type 1 diabetes and usually occurs later in life as the body gradually loses its ability to respond to insulin. Control of risk factors for cardiovascular disease already is a basic part of management of type 2 diabetes, since it is a major risk factor for such conditions as heart attack and stroke.

More information

The American Diabetes Association offers an overview of diabetic neuropathy.

SOURCES: Robert A. Rizza, professor, medicine, Mayo Clinic School of Medicine, Rochester, Minn.; Jayant Dey, M.D., endocrinologist, Ochsner Clinic Foundation, New Orleans; Jan. 27, 2005, New England Journal of Medicine

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