Nov. 25, 2008 -- Cardiac patients who are depressed are less likely to exercise, which increases their risk of a cardiac event such as a heart attack or heart failure, a new study suggests.
So heart patients who experience depression may be able to lower their cardiac risk simply by getting more physical activity.
It's long been recognized that patients who suffer from depression are more likely to have heart attacks or other cardiac events. But the reason for the association has been unclear. According to the new study, published in The Journal of the American Medical Association, the higher risk may be due to behavioral factors, especially physical activity levels.
Researchers looked at 1,017 heart disease patients. All were outpatients at clinics in the San Francisco area. They were recruited between 2000 and 2002, and followed until early 2008.
Participants completed a questionnaire to gauge whether or not they had depressive symptoms. Out of the group, 199 had depressive symptoms. The depressed patients were more likely to smoke, were less likely to take their medications as prescribed, and were less physically active.
Among the participants with depression, 10% had a cardiac event during the follow-up period. Among the non-depressed participants, 6.7% had a cardiac event. Cardiac events included heart failure, heart attack, stroke, transient ischemic attack (sometimes referred to as a "mini-stroke"), or death.
Even when the researchers made mathematical adjustments that accounted for other health issues and the severity of heart disease at the outset of the study, the group with depression was still 31% more likely to have a cardiac event than the group without depression. However, when lifestyle factors were also accounted for, there was largely no difference between the likelihood of a cardiac event for the depressed group and for the non-depressed group. In the final statistical model, the researchers found that physical inactivity alone was associated with a 44% greater rate of cardiovascular events.
"These findings raise the hypothesis that the increased risk of cardiovascular events associated with depression could potentially be preventable with behavior modification, especially exercise," the researchers write. "Exercise training can improve both depressive symptoms and markers for cardiovascular risk."
The researchers point out that their study could not discern whether depression led to inactivity or if inactivity led to depression. Regardless, the incorporation of exercise into a comprehensive depression treatment plan may be beneficial to many patients who suffer from both depression and heart disease.