Additionally, and just as importantly, the researchers said even a psychological status previously considered to be sub-depressive puts these patients at higher risk of death. While it has been known that depression is associated with higher short-term mortality rates, this is the first study to measure the long-term risks of depression, they said.
The researchers, led by medical psychiatrist Wei Jiang, M.D., believe that their findings should help convince physicians who care for heart failure patients to pay close attention to their patients' psycho-social status, since these patients may be helped by aggressive heart failure and/or antidepressant therapy.
Jiang presented the results of her study March 7, 2005, at the annual scientific sessions of the American College of Cardiology in Orlando. The study was supported by the National Institute of Mental Health.
"Our findings provide further evidence to non-psychiatric physicians that depression can have a major impact on how their patients fare," Jiang said. "Approximately half of all patients with heart failure will die within five years of diagnosis, and we believe that our study appears to identify a group of these patients who are at a higher risk for dying."
Heart failure is a condition marked by the inability of the heart muscles to pump enough oxygen and nutrients in the blood to the body's tissues. Also known as congestive heart failure, its many causes include infections of the heart, coronary artery disease, high blood pressure, previous heart attacks and valve problems. An estimated 4.7 million Americans suffer from the condition, with 400,000 new cases reported each year, and according to the researchers, it is the only cardiovascular disease that is rising in incidence.
The condition often leaves patients exhausted and breathless, severely restricting the normal activities of everyday life. Although there is no cure, a variety of drugs are often used to improve the strength of the heartbeat (digoxin), to relax blood vessels (ACE inhibitors), or to remove the excess buildup of fluid in the lungs (diuretics).
The Duke team followed 1,005 heart failure patients admitted to Duke University Hospital for various cardiac events. During their hospitalization, patients were given the Beck's Depression Inventory (BDI), a commonly used depression screening test. Patients were followed for seven years to determine the ability of BDI scores to predict death.
In general, patients with a BDI score of 10 are considered mildly depressed, while patients with scores of 12 to 19 can be considered mild to moderately depressed. Jiang said that the traditional cutoff value of BDI for assessing the prognostic predictability was a score of 10.
"In our group of patients, those who had a score of 10 or higher had a 44 percent greater risk of dying," Jiang said. "However, the greatest risk occurred when we lowered the threshold to a score of eight or greater. In our study, patients scoring seven or higher had a 51 percent higher risk of dying.
"This adverse association of depression and increased long-term mortality was independent of other factors, including age, marriage, cardiac function and the root cause of the heart failure," Jiang said.
Jiang said that many cardiologists or primary care physicians who treat heart failure patients may be unfamiliar with, or too busy to include, a psychological assessment into their practice. However, she pointed out, tests like the BDI do not require special training and can be completed in 10 minutes. Patients respond to 21 sets of questions with a number ranging from 0 to three.
For example, one such graded question set is: "I don't feel disappointed in myself - 0;" "I am disappointed in myself - 1;" I am disgusted with myself - 2;" or "I hate myself - 3."
"As you can see, it would not be difficult to get a score of eight or greater, pointing out how important it is to identify patients with depressive symptoms early and provide the appropriate treatment or support," Jiang said.
While this and other studies have demonstrated links between depression and worse outcomes for patients with cardiovascular disease, the mechanisms behind the correlation are not well understood, Jiang said. It is known that depressed patients have altered blood platelet aggregation properties, elevated immune-inflammatory responses and a decrease in the heart's ability to react appropriately to the stresses of everyday life, she said.
"We also know that depressed patients tend not to comply with their treatments, are not as motivated to stick with exercise or rehabilitation programs, and often miss doctor's appointments" Jiang said. "Also, depressed patients tend to make unhealthy life-style choices in such areas as diet and smoking."
While anxiety is often present with depression, previous studies by Jiang have shown that depression appears to be the main risk factor for these patients. In the Nov. 30 issue of the journal Circulation, Jiang found that while anxiety and depression are highly correlated in heart failure patients, depression alone predicts a significantly worse progrnosis after one year.
Jiang is currently investigating whether the use of anti-depressant medication has an effect on the outcomes of depressed heart failure patients.
Joining Jiang in the study were Duke colleagues Maragatha Kuchibhatla, Ph.D., Michael Cuffe, M.D.; Greg Clary, M.D., Eric Christopher, M.D., Jude Alexander, M.D., Ranga Krishnan, M.D., and Christopher O'Connor, M.D.