Study: Tight Glucose Control in Diabetes Lowers Risk of Atherosclerosis.


Strict glucose control in type 1 diabetes reduces the risk of atherosclerosis, a benefit that persists for years, according to a study published in the June 5, 2003, issue of The New England Journal of Medicine.

Since 1993, when the Diabetes Control and Complications Trial (DCCT) ended, researchers have known that intensive glucose control greatly reduces the eye, nerve, and kidney damage of type 1 diabetes. Now, researchers conclude, the benefits of tight control also extend to the heart.

"Intensive control is difficult to achieve and maintain, but its benefits are even greater than we realized," says study chair Saul Genuth, M.D., of Case Western University in Cleveland. "The earlier intensive therapy begins and the longer it can be maintained, the better the chances of reducing the debilitating complications of diabetes."

The DCCT was a multicenter study that compared intensive treatment with conventional management of blood glucose in 1,441 people with type 1 diabetes. Intensive treatment involves at least three insulin injections a day or an insulin pump and frequent self-monitoring of blood glucose. The goal of intensive treatment is to keep hemoglobin A1c (HbA1c), which reflects average blood sugar levels over 60 to 90 days, as close to normal (6 percent) as possible. Conventional treatment at the time of the DCCT consisted of one or two insulin injections a day with daily urine or blood glucose testing.

After six and one-half years of the DCCT, HbA1c levels averaged 7 percent in the intensively treated group and 9 percent in the conventionally treated group. When the DCCI ended, those who had been assigned to conventional treatment were encouraged to adopt intensive control and were shown how to do it. Researchers then began a long-term follow-up study of the participants, called the Epidemiology of Diabetes Interventions and Complications (EDIC) study

The DCCT could not study atherosclerosis because the participants were relatively young, and heart disease takes years to develop. In 1994-1995 and again in 1998-2000, EDIC researchers used ultrasound to measure the thickness of participants' carotid arteries, the two blood vessels in the neck that carry blood from the heart to the brain. Carotid wall thickness reflects the amount of atherosclerosis, or plaque build-up, in the artery. The thicker the arterial wall the greater the risk of later heart attack and stroke.

At the time of their first ultrasound, the diabetic participants' carotid wall thickness was similar to that of nondiabetic controls matched for age and gender. Five years later, however, the participants had thicker arterial walls than those of the non-diabetic group. In addition, the thickness of the carotid walls had increased less in the intensively treated group during the five years than in the conventionally treated group. "This finding strongly suggests that atherosclerosis progressed more slowly in the intensively treated group," noted Genuth.

Carotid thickening was also linked to known cardiovascular risk factors, including age, higher systolic blood pressure, smoking, LDL to HDL cholesterol ratio, and urinary albumin (a measure of kidney function). After adjusting for these factors, the researchers found that the differences in carotid wall thickness between the two groups were due to the differences in blood glucose levels during the DCCI.

"Now we know that intensively controlled glucose significantly reduces the atherosclerosis underlying heart disease just as it reduces damage to the eyes, nerves, and kidneys in people with type 1 diabetes, " says David Nathan, M.D., of Massachusetts General Hospital, who co-chaired the DCCT-EDIC research group. "What's striking is that the benefits of intensive control persisted, despite a gradual rise in the HbA1c levels of the intensively treated group during the five years after DCCI' ended."

Diabetes prevention is a major initiative of the Department of Health and Human Services.

About 17 million people in the United States have diabetes. About I million have type 1 diabetes. Formerly known as juvenile onset or insulin-dependent diabetes, type 1 diabetes usually begins in children and adults under age 30.

Type 2 diabetes accounts for up to 95 percent of all diabetes cases. Most common in adults over age 40, type 2 diabetes affects 6 percent of the U.S. population. It is strongly associated with obesity (more than 80 percent of people with type 2 diabetes are overweight), inactivity, and family history of diabetes, and is higher in some racial or ethnic groups. The prevalence of type 2 diabetes has tripled in the last 30 years, due in large part to the upsurge in obesity.

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