A recent report in the New England Journal of Medicine describes the cardiovascular benefits of rigorous control of blood glucose by those with diabetes. The report focuses on a fairly simple and extremely important indication: that rigorous control of blood glucose levels not only reduces the best known complications of diabetes – damage to the eyes, nerves and kidneys – but that it also greatly reduces the incidence of heart disease in this disease population. Previous reports issued at conferences of the American Diabetes Association (ADA; Alexandria, Virginia) have pointed to the value of good glucose control for reducing heart disease in this population. But publication in NEJM results in broader dissemination to the public through general news outlets. In summary, the study showed that tight glucose control lowers the risk of cardiovascular disease events by 42% and the risk of a serious event, such as heart attack or stroke, by 58%.
The findings reported in the NEJM story are based on a follow-up study of patients who took part in long term research termed the Diabetes Control and Complications Trial (DCCT) – a study funded by the National Institutes of Health (NIH; Bethesda, Maryland) and its National Institute of Diabetes and Digestive Kidney Disease (NIDDK) unit – and launched about 20 years ago. DDCT involved 1,441 people in a comparison of intensive vs. conventional control of blood glucose, with the initial results rolled out in 1993 and indicating a large reduction (from 39% to 76%) in the development of microvascular complications such as retinopathy, neuropathy and nephropathy. Then a study of DDCT participants released in 2003 showed that steady glucose control had the effect of reducing atherosclerosis. As a subset of the DDCT study, a large majority of the participants (1,375) in DDCT then were enrolled in the Epidemiology of Diabetes Interventions and Complications (EDIC) study, which went on to make annual assessments over an eight year period and has served to produce the more definitive results concerning reduction of heart disease and the lowered occurrence of angina, heart attack and stroke. “We see a greater reduction in cardiovascular events from intensive blood glucose control than from drugs that lower blood pressure and cholesterol,” said Saul Genuth, MD, of Case Western University (Cleveland), chair of the EDIC study.
Besides demonstrating the overall value of strict glucose control for reducing serious cardiovascular events, the study produced a sort of sub category of interesting and clinically important outcomes, chiefly:
That early good control of blood glucose levels had long lasting effects. The benefits of the first six years of intensive control persisted even though the blood glucose level of the intensively treated group had gradually risen to a HbA1c reading of about 8%, matching to that of the conventionally treated group, which had declined.
And that intensive control of blood glucose may be as important for those with Type 2 diabetes (the less serious type of the disease) as those with Type 1 diabetes. Indications that glucose control produced lower rates of heart disease in Type 2 sufferers has been assumed for some time, but the new data indicates that these advantages are relevant for all of those with the disease.
This concept could be better established in another study, the Action to Control Cardiovascular Risk in Diabetes (ACCORD), which will test ways to lower the risk of heart disease and stroke in adults with Type 2 diabetes, sponsored by NIDDK and the National Heart, Lung, and Blood Institute. Results of this study are slated to be released in 2009. In the initial DCCT study, patients 13 to 39 years of age were randomly assigned to intensive treatment, which meant attempting to keep glucose levels as close to normal as possible – hemoglobin A1c (HbA1c) readings at 6% or less with at least three insulin injections a day or an insulin pump, guided by frequent self monitoring of blood glucose. (HbA1c reflects average blood glucose over the past two to three months.)
At the end of the study, HbA1c readings averaged 7% in the intensively treated group and 9% in the conventionally treated patients, who were then encouraged to adopt intensive control and shown how to do it. The NIH said that these findings prompted “a major shift” in the way doctors manage their patients with Type 1 diabetes. Among the 1,375 volunteers who continued continuing to participate in the study, the intensively treated patients had 46 cardiovascular disease CVD events, compared to 98 such events for the conventionally treated group. Thirty-one intensively treated patients (4%) and 52 conventionally treated patients (7%) had at least one CVD event during the average 17 years of follow-up from the start of the DCCT. The average age of participants is now 45 years, slightly more than half of them males. <>Nearly 21 million people in the U.S. – 7% of the population – have diabetes, and at least 65% of those with diabetes will die from a heart attack or stroke. But the ADA says that two out of every three with diabetes are unaware of their increased risk. Type 1 diabetes accounts for 5% to 10% of diagnosed cases of diabetes in the U.S. (up to 1 million people). This form of diabetes usually strikes children and young adults, who need three or more insulin injections a day or treatment with an insulin pump to maintain the level of blood glucose control shown to prevent or delay long term complications.