Depressed heart attack patients have a higher risk for sudden death in the months following a heart attack. Now a team led by School of Medicine researchers has found that the risk continues for many years.
“There’s a two- to four-fold increase in a person’s risk of dying following a heart attack if they also happen to be depressed,” said Robert M. Carney, Ph.D., lead author of the study and professor of psychiatry. “Previously we thought the impact of depression was strongest for the first three to six months following a heart attack and then gradually dropped off within a couple of years. Instead, we found that the effect lasts for at least five years.”
Carney, with colleagues from Duke University Medical Center, Harvard University, Yale University, the National Heart, Lung, and Blood Institute of the National Institutes of Health (NIH) and the Mayo Clinic, followed more than 750 heart attack patients for five years. The findings will appear in an upcoming issue of the Journal of Affective Disorders and are available online.
Patients followed in the study had participated in the NIH-funded project “Enhancing Recovery in Coronary Heart Disease Patients.” Just under half were diagnosed with depression.
In the five years following a heart attack, 106 patients died. Of those, 62 had been diagnosed with depression. In gauging the effects of depression, the investigators also considered other risks including age, smoking, hypertension, gender and diabetes.
Some of those factors, such as younger age and female gender, lower mortality risk. Smoking and diabetes tend to raise the risk of dying. Carney said his team used statistical methods to evaluate the ways in which the various factors influenced mortality risk. Then they removed the influence of all other factors from the risk equation in order to consider the statistical impact of depression itself.
“We found that after adjusting for those risk factors, depression continues to play a statistically significant role,” Carney said.
One possible explanation for depression’s lingering influence on mortality is its recurring nature. Because the disorder can come and go over many years, it also may continue to increase the risk of death for many years.
“People typically are depressed for a while, then they’ll either get better with treatment or it may subside on its own,” Carney said. “But depression can always recur, and we think that, because it is a recurring problem, whatever depression is doing to mortality risk after a heart attack, it continues doing for quite a long time.”
Past studies have differed over how much depression affects survival following a heart attack. But Carney said these new findings are more reliable because all of the patients in this study were personally interviewed to determine their depression status, whereas other studies have relied on self-reporting, which can overestimate the risk.
Carney’s team also found that any clinically relevant depression increases the risk of death in heart attack patients. The risk was elevated both for patients with major depression, which requires the presence of five or more symptoms, and minor depression, which requires between two and four symptoms for diagnosis. Major depression was associated with higher risk, but mi-nor depression also was associated with a significant increase in mortality risk.
Even with mounting evidence of a link between depression and death in heart attack patients, only about 25 percent to 30 percent of these patients receive antidepressant drugs or other depression treatments.
That doesn’t surprise Carney. His team reported in 2003 in the Journal of the American Medical Association that providing treatment for depression seemed to have little effect on whether patients survived or had a second heart attack. This could be because the treatments don’t work for all patients, Carney said, and he suggests if current depression treatments could be improved, survival rates might increase, too.
To this end, his team is studying whether omega-3 fatty acids — the fatty acids found in fish oil — might improve antidepressant therapies in heart patients. They’re giving an antidepressant drug and a special formulation of omega-3 to some heart patients and comparing them to depressed heart patients who receive an antidepressant but no omega-3.
“We have not been satisfied with the effectiveness of standard antidepressants at alleviating depression in this population of patients,” Carney said. “We’re studying omega-3 because there’s preliminary evidence that the fatty acids also might make depression therapies more effective, both in treating depression and in improving heart health.”
The new study is enrolling people with depression who have suffered a heart attack at least three months previously. After being evaluated for depression, patients will take an antidepressant and be randomly assigned to take a capsule containing either omega-3 or corn oil for 12 weeks. Carney’s team evaluates both mood and heart function during the course of the study.
All medication, supplements, medical and psychiatric evaluations are provided at no charge. For more information about the study, call Cathi Mueller at 286-1517 or Carol Sparks at 286-1315.