June 11, 2008 (San Francisco) — People with type 2 diabetes who tightly control their blood sugar to lower-than-recommended levels have no greater heart benefits than those who use standard therapy, according to a study of U.S. veterans. It was the third major study of heart disease prevention presented this week at the American Diabetes Association meeting in San Francisco, and all had similar findings.
Unlike the others, the veteran study did suggest that controlling blood pressure and cholesterol could result in fewer strokes and heart attacks in older, sicker patients (see "Why Diabetes Boosts the Risk of Strokes and Heart Attacks").
"We predicted ahead of time the number of incidents (of heart attack and stroke) we would have, and with our excellent blood pressure and lipid control…we did not come anywhere near the number we had predicted," says William C. Duckworth, MD, director of diabetes research at the Carl T. Hayden VA Medical Center in Phoenix and co-chair of the study. "This trial reduced all kinds of incidents rather largely. We did good overall."
In the VA Diabetes Trial, researchers are following more than 1,700 veterans. At the start of the study, the patients had an average hemoglobin A1C score of 9.5%. (The American Diabetes Association recommends an A1C of less than 7%.) All the patients had multiple health problems: 40% had prior cardiovascular events, 80% had hypertension, and more than 50% had cholesterol problems.
The researchers split patients into standard and intensive glucose control groups, and aimed to lower blood pressure and cholesterol in both. Within six months the standard group achieved an average of 8.4% hemoglobin A1C, while the more intensive group reached 6.9%.
There was no difference between the two groups in terms of heart attacks and strokes. However, both groups had a fewer-than-expected number of cardiovascular events, presumably due to their better diets, more exercise, aspirin use, and efforts to lower cholesterol compared with their peers in the general population. The researchers expected 650 and 700 events in the standard and intensive therapy groups, respectively, but there were only 263 and 231 heart attacks and strokes.
Carlos Abraira, MD, professor of medicine at the Miami VA Medical Center and a principal investigator of the study, said doctors will continue to follow patients for another nine years to see if there are any long-term benefits of tight blood sugar control. "We want to see if there are no fatal events and other favorable effects of glycemic control that might be expressed later on," Dr. Abraira says.
The study had another important finding. The researchers found a link between severe low blood sugar events and cardiovascular events, Dr. Duckworth said. Severe hypoglycemia (altered consciousness or loss of consciousness) was a major predictor of stroke, heart attack, and death in the study.
"A severe hypoglycemic episode within three months prior was predictive of a cardiovascular event," Dr. Duckworth said.
The two earlier studies released at the meeting, ACCORD and ADVANCE, also failed to show that intensive blood glucose control could help cut cardiovascular risk. In ACCORD, researchers actually had to halt aggressive therapy after patients were shown to have a higher risk of death than those with standard treatment.
The authors of all three studies say, however, that reducing blood sugar to recommended levels has been shown to lower the risk of diabetes complications such as vision loss, kidney failure, and nerve damage. And it’s still not clear if more aggressive treatment may offer some heart benefits to certain patients (e.g., those without existing heart disease) or may work with some drugs but not others.
By Sean Kelley