People with advanced heart failure and who also have diabetes that requires insulin treatment have about a fourfold greater mortality rate than heart failure patients who don’t take insulin, researchers report.

“The magnitude of the effect was pretty surprising,” investigator Dr. Gregg C. Fonarow from the Ahmanson-UCLA Cardiomyopathy Center in Los Angeles said in a telephone interview with AMN Health.

Previous studies have shown that diabetes itself is associated with a moderate increase in mortality risk in heart failure patients. “But none of these prior studies have really looked at the way the diabetic patients had been treated with regard to insulin and oral medications, so this really is a new and dramatic finding,” Fonarow explained.

Fonarow’s team followed a group of 554 patients with advanced heart failure, of whom 132 had diabetes. Of these, about a third were on insulin therapy while the rest used other, oral medications or diet restrictions to control blood sugar levels.

One-year survival rates were 90 percent for non-diabetic patients, 86 percent for non-insulin-treated diabetic patients, but only 62 percent for insulin-treated diabetic patients, the investigators report in the American Heart Journal.

After taking into account differences in age and patients’ medical history, analysis of the data showed that insulin therapy was a predictor of mortality and “highly statistically significantly so,” Fonarow said. Non-insulin treated diabetes did not increase the risk of dying.

“We can’t be sure that it is the insulin itself leading to this dramatic increase in mortality risk,” he continued, “but certainly there is an urgent need for further investigation to see whether we should try to avoid insulin in these patients.”

“In the near term,” Fonarow concluded, “clinicians need to recognize that heart failure patients with diabetes who are treated with insulin are at particularly high risk for mortality and deserve increased attention.”

SOURCE: American Heart Journal, January 2005.