The study, by a team of UCLA scientists, will be published in the January issue of the American Heart Journal.

Researchers assessed the history of diabetes and insulin treatment in 554 patients with advanced heart failure after adjusting for various risk factors. One year survival rates were 89.7 percent for non-diabetic patients, 85.8 percent for non-insulin-treated diabetic patients, and only 62.1 percent for insulin-treated diabetic patients.

Heart failure affects 5 million in the United States and is the most common cause of hospitalization for those 65 years and older. Between 25 percent and 44 percent of heart failure patients also have diabetes.

"Further studies into what is the best strategy to control blood sugar levels in patients with diabetes and heart failure are urgently needed," said one of the investigators.