STOCKHOLM (Reuters) - Patients with chronic heart failure given injections of their own bone marrow stem cells have better heart function and live longer, German researchers said Sunday.

The beneficial effects of the cell therapy were seen within three months and continued for five years, according to findings from one of the biggest studies to date on using stem cell therapy to treat heart conditions.

For years, doctors have tried to use various forms of stem cells to treat damaged hearts, with varying results.

The latest findings are still not conclusive but lead researcher Bodo-Eckehard Strauer of Duesseldorf's Heinrich Heine University said the long-term benefits were encouraging.

Previous studies have suggested that cell therapy can be effective in patients who have suffered a heart attack. The new research indicates it could also play a role in patients with chronic heart failure.

Bone marrow stem cells used in the study were taken from the top of the patient's pelvis and sorted in the lab before being injected back into the heart area, where they improved ventricular function, or the heart's ability to pump blood.

The study included 391 patients, of whom 191 agreed to have the bone marrow stem cell treatment and 200 did not. After five years, seven patients had died in the treated group against 32 in the control arm -- a significant difference.

"Our study suggests that, when administered as an alternative or in addition to conventional therapy, bone marrow cell therapy can improve quality of life, increase ventricular performance and increase survival," Strauer said.

Heart failure occurs when the heart muscle loses its ability to pump blood through the body efficiently, often as a result of a heart attack.

Conventional drug-based treatments do not attempt to correct the underlying cause, which is usually the loss of functional heart tissue, and the prognosis for the treatment is poor.