Intensive glucose control lowers the risk of heart disease and stroke by about 50 percent in people with type 1 diabetes. Researchers announced this finding after analyzing cardiovascular disease (CVD) events such as heart attack, stroke, and angina in patients who took part in the Diabetes Control and Complications Trial (DCCT).
Saul Genuth, MD, of Case Western Reserve University Medical School, heads the follow-up study, called the Epidemiology of Diabetes Interventions and Complications (EDIC) study. This follow-up study is now examining the long-term effects of prior intensive management versus conventional blood glucose control.
About the Study
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 levels as close as possible to the normal value of six percent or less. (The A1c blood test reflects a person’s average blood sugar over the past two to three 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.
Long-lasting Benefits
After six and a half years of the DCCT, A1c levels averaged seven percent in the intensively treated group and nine 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 six years of intensive control have persisted despite the fact that both groups' A1c values have leveled off at about eight 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, tight glucose control lowered the risk of a CVD event by 42 percent and the risk of a serious event, including heart attack or stroke, by 58 percent. 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 (four percent) and 52 conventionally treated patients (seven 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, MD, of Massachusetts General Hospital, who co-chaired the DCCT/EDIC research group and presented the results. “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.”
“The take-home message is that good glucose control should be started as early as possible to delay or prevent serious diabetes-related complications,” said Alan D. Cherrington, PhD, past president of the American Diabetes Association.
What About Type 2 Diabetes?
Is glucose control just as important for people with type 2 diabetes? “There is a strong and growing body of evidence that everyone with diabetes gains from strict blood glucose control,” said Catherine Cowie, PhD, who oversees EDIC for the National Institute of Diabetes and Digestive and Kidney Diseases.
About 20.8 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.
Type 1 diabetes accounts for up to 10 percent of diagnosed cases of diabetes in the United States (about 2 million people). This form of diabetes usually strikes children and young adults who need several insulin injections a day or an insulin pump to survive. Insulin, though critical for controlling blood glucose, is no cure. Most people with type 1 diabetes eventually develop one or more complications, including damage to the heart and blood vessels, eyes, nerves, and kidneys.
Resources:
Be Smart About Your Heart: Control the ABCs of Diabetes encourages people with diabetes to control their blood glucose as well as their blood pressure and cholesterol. By keeping all three as close to normal as possible, people with diabetes can live long, healthy lives.
Make the Link! Diabetes, Heart Disease and Stroke works to increase awareness of the link between diabetes and heart disease and help educate physicians and people with diabetes about how to reduce those risks. |
