Each year, 5 million people suffer heart failure in the U.S. According to the Centers for Disease Control and Prevention, treating these patients cost over $100 billion in 2010.

Many risk factors can lead to heart failure, including high blood pressure, high cholesterol, diabetes and obesity.

According to an international study led by researchers from Duke University, depression may contribute as well.

In a paper published in August in the Journal of the American Medical Association, James Blumenthal and his colleagues found that depression can worsen heart disease, and may help cause heart disease in healthy individuals.

“There is good evidence that depression increases the risk of heart disease in healthy people,” Blumenthal, a professor of psychiatry and behavioral science, said in an interview. “In our study (it was found that) patients with heart failure – and with elevated depressive symptoms – were more likely to die or to be hospitalized, compared to those who were not depressed,” Blumenthal said.

“Additionally, for patients who experienced a worsening of depressive symptoms, their risk (of death or hospitalization) was further increased.”

Luckily, exercise may help.

The team studied two groups of heart failure patients, who were randomly assigned one of two groups: supervised exercise sessions for three months followed by home-based exercise, or to standardized care without an explicit exercise prescription. In examining the data, the exercise group showed reduced depression and improved heart health.

The results lend support for regular exercise as a standard of care. If patients’ mental and physical health improve with exercise, they may be less likely to require extensive medical treatment, reducing health care costs.

“Exercise should be recommended for all heart-failure patients, who can safely exercise,” said Blumenthal, “and it is quite possible that long-term medical costs would be reduced.”

Blumenthal notes these potential cost savings are an issue for future research. The team is now conducting a new study, also sponsored by the National Institutes of Health, to determine whether exercise and diet can improve memory and other cognitive abilities in patients with heart disease who also are at risk for developing dementia.

Blumenthal concedes there are risks to physical activity, but notes the positive benefits cannot be ignored.

“Heart failure patients can experience abnormal cardiac responses. But our study showed that with proper safeguards and medical supervision, exercise is safe for most patients, and that the benefits outweigh the risks.”