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Diabetes mellitus type 1: tight glucose control lowers risk of heart disease

A tight glucose control in people with type 1 diabetes can reduce significantly the risk of heart disease.

This finding is based on analysis of the 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 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.
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 6½ 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.

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.

“ The risk of heart disease is about 10 times higher in people with type 1 diabetes than in people without diabetes. It’s now clear that high blood glucose levels contribute to the development of heart disease,” said David Nathan, of Massachusetts General Hospital, who co-chaired the DCCT/EDIC research group.“ The good news is that intensively controlling glucose significantly reduces heart disease as well as damage to the eyes, nerves, and kidneys in people with type 1 diabetes. Tight control is difficult to achieve and maintain, but its advantages are huge.”

About 18.2 million people in the United States have diabetes, the most common cause of blindness, kidney failure, and amputations in adults and a major cause of heart disease and stroke. At least 65 percent of people with diabetes will die from a heart attack or stroke, yet two out of every three people with diabetes are unaware of their increased risk.

Source: National Institute of Health, 2005