Patients who become depressed after a major heart-related event, such as a heart attack, have a significantly higher risk of dying than those who are not depressed, a study finds, but cardiac rehabilitation and exercise training can substantially reduce depression and the associated mortality.

Depression and depressive symptoms develop in up to 20 percent of patients with heart disease and depression remains an "underappreciated as a coronary risk factor," note Dr. Richard V. Milani and Carl J. Lavie, from Ochsner Medical Center, New Orleans, Louisiana.

They took a look back at the impact of cardiac rehabilitation on depression and subsequent long-term mortality in 522 patients with coronary artery disease. The patients, who were an average of 64 years old, completed cardiac rehabilitation between January 2000 and July 2005. The investigators compared these patients with control group of 179 coronary artery disease patients who did not complete rehabilitation.

Of the 522 patients in the rehab group, 91 (17 percent) had depressive symptoms at the outset. The prevalence of depression decreased a significant 63 percent, from 17 percent to 6 percent, following rehabilitation.

Death rates were 4-fold higher among depressed patients following rehabilitation compared to non-depressed patients (22 percent versus 5 percent). However, depressed patients who completed cardiac rehabilitation had a nearly 4-fold decrease in mortality compared with depressed patients who did not complete cardiac rehabilitation (30 percent versus 8 percent).

The decline in depression, and associated mortality, was linked to improvements in fitness, according to the authors. However, similar improvements in depression were observed in patients with modest and substantial increases in exercise ability.

"Depression is a prevalent risk factor and is modifiable," Milani concluded in an interview with Reuters Health.