Depression is the strongest predictor of death in the first decade following a diagnosis of coronary heart disease, according to a new study by researchers at the Intermountain Medical Center Heart Institute in Salt Lake City.
The study, which is scheduled for presentation this week at the American College of Cardiology's 66th Annual Scientific Session in Washington, D.C., found people with coronary heart disease who are diagnosed with depression are about twice as likely to die compared with those who are not diagnosed with depression.
"Our study shows that it doesn't matter if depression emerges in the short term or a few years down the road - it's a risk factor that continually needs to be assessed," said Heidi May, PhD, MSPH, a cardiovascular epidemiologist at the Intermountain Medical Center Heart Institute in Salt Lake City, and the study's lead author. "I think the take-home message is that patients with coronary disease need to be continuously screened for depression, and if found to be depressed, they need to receive adequate treatment and continued follow-up."
The Intermountain Medical Center Heart Institute study focused on patients diagnosed with a heart attack, stable angina or unstable angina, all of which are caused by a reduced flow of oxygen-rich blood to the heart, typically as a result of plaque buildup in the heart's arteries. These conditions fall under the umbrella term coronary heart disease, which is the most common form of heart disease and kills about 370,000 people in the United States annually.
Researchers have long understood heart disease and depression to have a two-way relationship, with depression increasing the likelihood of heart disease and vice versa. Whereas previous studies have investigated depression occurring within a few months of a coronary heart disease diagnosis, this new study is the first to shed light on the effects of depression over the long term.
"The majority of studies evaluating depression following a heart disease event have occurred within 30 days of the event," said May. "We sought to determine if the risk of all-cause mortality associated with depression varies with time between the diagnosis of heart disease and a follow-up depression diagnosis."
The research team analyzed health records from almost 25,000 Intermountain Healthcare patients tracked for an average of nearly 10 years following a diagnosis of coronary heart disease. About 15 percent of patients received a follow-up diagnosis of depression, a substantially larger proportion than the estimated rate of 7.5 to 10 percent in the general population.
Out of 3,646 people with a follow-up diagnosis of depression, half died during the study period, compared to 38 percent of the 20,491 people who did not have a depression diagnosis. This means people with depression were twice as likely to die compared to those without depression.
May says the results were surprising.
"I thought depression would be significant, but not the most significant predictor," she added.
After adjusting for age, gender, risk factors, other diseases, heart attack or chest pain, medications and follow-up complications, the results showed depression was the strongest predictor of death in this patient group. These results were consistent regardless of age, gender, the timing of depression onset, past history of depression or whether or not the patient had a heart attack.
Given the significant impact of depression on long-term survival, the researchers said clinicians should seek ways to better identify depression in patients with coronary heart disease, either by using patient questionnaires designed to screen for depression or by actively watching for signs of depression during follow-up examinations.
"It can be devastating to be diagnosed with coronary artery disease," May said. "Clinicians need to pay attention to the things their patients are expressing, in terms of both physical symptoms as well as emotional and nonverbal factors."
Signs of depression include persistent feelings of sadness, hopelessness or worthlessness; anxiety, irritability or restlessness; losing interest in hobbies and activities; fatigue or moving slowly; difficulty sleeping or concentrating; aches or pains without a clear physical cause; changes in appetite or weight; and thoughts of death or suicide.
Depression is linked with behaviors that can be detrimental to cardiovascular health, such as reduced physical activity, poor diet, increased smoking or alcohol use and reduced compliance with medical treatment.
"There is a lot more research that needs to be done with depression and heart disease, May said. "Moving forward, we would like to further assess treatment affects, severity of symptoms, and other comorbidities that may put a patient at an increased risk of death.