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Intensive Blood Sugar Control in Type 2 Diabetes

People with type 2 diabetes, particularly those at risk for heart attack and stroke, need to keep their blood sugar from getting too high. But a new study of adults with type 2 diabetes at high risk for cardiovascular problems found that tighter control isn't always better. A therapeutic strategy to tightly control blood sugar not only failed to reduce their risk of major cardiovascular events; it actually raised their risk of death.

An estimated 21 million Americans have diabetes, and 284,000 die from it each year. Cardiovascular conditions account for 65% of those deaths. In fact, adults with type 2 diabetes are more than twice as likely as those without diabetes to die from heart disease.

Previous studies suggested that keeping blood sugar at near-normal levels might help people with type 2 diabetes lower their risk for cardiovascular disease. However, these observational studies didn't actually test treatments to reduce blood sugar. Blood sugar control has been shown in clinical trials to reduce some complications from diabetes, including eye and kidney diseases. It also lowers cardiovascular disease risk in people with type 1 diabetes.

The ACCORD (Action to Control Cardiovascular Risk in Diabetes) clinical trial, which was supported primarily by NIH's National Heart, Lung and Blood Institute (NHLBI), set out to compare a strategy aiming for near-normal blood sugar levels—below both current recommendations and those tested in previous studies—to the standard blood sugar targets for people with type 2 diabetes and heart disease or other cardiovascular risk factors. Conducted at 77 sites in the U.S. and Canada, ACCORD enrolled over 10,000 people between the ages of 40 and 79. The participants, who had been living with diabetes for an average of 10 years, were randomly assigned to standard or intensive treatment goals. Both groups received patient education and counseling and were treated with FDA-approved diabetes medications as needed to reach the treatment goals.

In February, NHLBI stopped the intensive blood sugar strategy early, after an average of 3.5 years of treatment instead of the planned 5.6 years, because of safety concerns. The first published results, in the June 12, 2008, issue of the New England Journal of Medicine, show that the intensive strategy group had a 22% higher risk of death—or 54 more deaths—than the standard group. The causes of death were similar in each group, with about half from cardiovascular conditions, such as heart attack, sudden cardiac death, stroke or heart failure.

"Despite detailed analyses, we have been unable to identify the precise cause of the increased risk of death in the intensive blood sugar strategy group," noted lead author Dr. Hertzel C. Gerstein. "We believe that some unidentified combination of factors tied to the overall medical strategy is likely at play."

For adults with long-standing type 2 diabetes who have or are at risk for cardiovascular disease, intensively lowering blood sugar to near-normal levels appears to be too risky. It's not yet clear whether it could help patients at lower risk of cardiovascular disease or those with more recently diagnosed type 2 diabetes.

All ACCORD study participants now aim for standard blood sugar levels. Other components of the study—looking at aggressively lowering blood pressure and treating multiple blood lipids (cholesterol and triglycerides) in high-risk diabetic patients—are continuing through June 2009.