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By Anne Harding

TUESDAY, Nov. 25, 2008 (Health.com) — It’s long been known that heart patients who are depressed are at greater risk of heart attack, stroke, and death than their happier peers, and now a new study sheds light on the reasons why.

The risk seems to be due to a patient’s behavior, rather than some mysterious biological factor or other problem, as some have theorized. Depressed people who have heart disease are more likely to smoke, less likely to take their medicine, and—the biggest problem—are less likely to exercise than nondepressed heart patients, according to the report in the Journal of the American Medical Association.

“The good news for patients is that it’s all about behavior,” says Mary A. Whooley, MD, of the Veterans Affairs Medical Center in San Francisco. Dr. Whooley was the lead researcher on the study, which followed 1,017 people with stable heart disease for nearly five years.

“That means that the link is modifiable and there’s something they can do about it," she says.

The bad news? It’s all about behavior. “It’s so hard for people to change their behavior, and especially for depressed patients because they have so much less motivation to take care of themselves,” Dr. Whooley explains.

And it seems to be a vicious cycle. People who are depressed are more likely to develop heart disease in the first place, and people who have a heart attack are (not surprisingly) at risk for depression. Depression can also hamper recovery from heart surgery or heart failure.

Researchers have proposed numerous factors to explain the complex interplay between mood, stress, and cardiovascular health: Examples include behavior and biological factors such as inflammation; some experts even think that antidepressants are bad for the heart.

To dig deeper, Dr. Whooley and her team looked at people—mostly older men—with confirmed, stable heart disease, and assessed various measures of heart disease severity as well as hormones, inflammation markers, and even levels of omega-3 fatty acids.

“We spent a lot of time and effort and money measuring all sorts of fancy biomarkers,” Dr. Whooley says. “We thought for sure one of those was going to explain the link. We were really surprised that it was such a simple answer.”

Next: One in five people in the study were depressed

In all, 19.6% of patients had symptoms of depression and they were indeed at greater risk of having a cardiac event, defined as a heart attack, stroke, a mini-stroke (known as a transient ischemic attack), heart failure, or death due to cardiovascular causes.

Annually, 1 in every 10 depressed patients had a cardiac event, compared to 1 in 15 nondepressed patients. After the researchers accounted for the severity of a patient’s heart disease, as well as the presence of other illnesses such as diabetes, depression still boosted cardiac event risk by 31%.

But when the researchers threw physical activity into the equation, they found the depression–cardiac event link nearly disappeared, suggesting that most of the increased risk seen in the depressed people was due to their lack of exercise. Skipping medication and smoking also helped account for the link.

“Yes, they’re at higher risk, but their risk seems to be driven by these other unhealthy activities [and] behaviors, rather than depression per se,” says Gregg Fonarow, MD, a professor of medicine at the University of California–Los Angeles and codirector of UCLA’s Preventative Cardiology Program. The findings help explain why studies investigating antidepressants or social support to help ease depression in people with heart disease have had disappointing results, he adds: “Treating depression may not in and of itself lower cardiovascular risk in these patients.”

Next: What you should do if you're depressed

So what can be done to help depressed heart patients take their pills, quit smoking, and become more active? Cardiac rehabilitation programs, which include counseling on exercise, nutrition, medication use, and coping with stress, are one strategy that has been shown to help people change their behavior. But while national guidelines recommend cardiac rehab for anyone who’s had a heart attack, and Medicare covers it, use of such programs is far from universal among the people who could benefit from them. (Medicare also pays for cardiac rehab for heart disease patients with angina or people who have had bypass surgery.)

“The problem is many patients don’t adhere to the recommendations, or the prescription isn’t provided by the physician,” Dr. Fonarow says.

Patients should go to cardiac rehab three times a week, a frequency which goes a long way toward helping them build healthier habits, according to Janet S. Wright, MD, senior vice president for science and quality at the American College of Cardiology in Washington, D.C. “It’s definitely underutilized and it’s one of the most effective programs we have,” she says.

The first step a depressed person with heart disease should take is to recognize that they are under stress and get help, Dr. Wright says. Becoming more active can start with just heading out the door for a brisk walk around the block. Intensity and quantity of exercise aren’t as important as consistency, Dr. Wright points out.

Getting more exercise is a well-known antidote for depression, if you can muster the will to get moving.

“You literally treat depression with exercise the same way you would with an antidepressant. It has to be taken daily,” says Dr. Wright.


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