Glucose control could lower risk of heart disease in diabetics

14/06/05 A significantly lower risk of heart disease can now be added to the list of proven long-term benefits of tight glucose control in people with type 1 diabetes. Researchers announced this finding at the annual scientific meeting of the American Diabetes Association after analyzing cardiovascular (CVD) events such as heart attack, stroke, and angina in patients who took part in the Diabetes Control and Complications Trial (DCCT) years ago.

"The longer we follow patients, the more we're impressed by the lasting benefits of tight glucose control," said Saul Genuth, M.D., of Case Western University. Dr. Genuth chairs the follow-up study of DCCT participants, called the Epidemiology of Diabetes Interventions and Complications (EDIC) study, which has been looking at the long-term effects of prior intensive versus conventional blood glucose control. "The earlier intensive therapy begins and the longer it is maintained, the better the chances of reducing the debilitating complications of diabetes."

The DCCT was a multicenter study that compared intensive management of blood glucose to conventional control in 1,441 people with type 1 diabetes. Patients 13 to 39 years of age were enrolled in the trial between 1983 and 1989. Those randomly assigned to intensive treatment kept glucose levels as close to normal as possible with at least three insulin injections a day or an insulin pump, guided by frequent self-monitoring of blood glucose. Intensive treatment meant keeping hemoglobin A1c (HbA1c) levels as close as possible to the normal value of 6 percent or less. (The HbA1c blood test reflects a person's average blood sugar over the past 2 to 3 months.) Conventional treatment at the time consisted of one or two insulin injections a day with daily urine or blood glucose testing.

In 1993, researchers announced the DCCT's main findings: intensive glucose control greatly reduces the eye, nerve, and kidney damage of type 1 diabetes. Tight control also lowers the risk of atherosclerosis, according to a study of DCCT participants published in 2003. But what's most remarkable about intensive control, the researchers say, is its long-lasting value.

After 61/2 years of the DCCT, HbA1c levels averaged 7 percent in the intensively treated group and 9 percent in the conventionally treated group. When the study ended, the conventionally treated group was encouraged to adopt intensive control and shown how to do it, and researchers began the long-term follow-up of participants. To the researchers' surprise, the benefits of the original 6 years of intensive control have persisted despite the fact that both groups' HbA1c values have leveled off at about 8 percent after a rise in blood glucose in the intensively treated group and a drop in blood glucose in those formerly on conventional treatment.

In results announced, among the 1,375 volunteers continuing to participate in the study, the intensively treated patients had less than half the number of CVD events than the conventionally treated group (46 compared to 98 events). Such events included heart attacks, stroke, angina, and coronary artery disease requiring angioplasty or coronary bypass surgery. Thirty-one intensively treated patients (4 percent) and 52 conventionally treated patients (7 percent) had at least one CVD event during the 17 years of follow- up. The average age of participants is 45 years; 53 percent are male.