While the finding isn't surprising, the review gives a clearer picture of the relevant research to date.

"Everybody knows that stress is bad for your heart... but the evidence has been scattered out over the years," said Donald Edmundson, a professor at Columbia University Medical Center and one of the authors of the study.

Starting with a large British study from the 1960s that found an increased heart disease risk among poor people, researchers have linked stress to poor heart health.

And just this year, a study of 200,000 people in Europe showed that those who have stressful jobs are more likely to receive a diagnosis of heart disease than people whose jobs are less demanding and offer more freedom (see Reuters report of September 14, 2012).

To get a better grasp of what the research has had to say about people's own perception of stress and their heart disease risk, Edmundson and his colleagues gathered the results of six large studies on the topic.

Nearly 118,000 people participated in the studies, which surveyed the participants about the stress in their lives.

Some studies used a scale of how frequently or how severely the people felt stressed out, while others used a simple yes or no response to the question of whether someone had felt stressed.

At the beginning of the studies, none of the participants had been diagnosed with heart disease.

Over follow-up periods - anywhere from three to 21 years - the researchers tracked how many of those surveyed developed coronary heart disease, a condition in which the heart's arteries narrow due to cholesterol-rich deposits. Eventually, the buildups can snag the blood flow to the heart and cause heart attacks.

According to the National Institutes of Health, coronary heart disease is the number one killer of men and women in the U.S., with more than 400,000 people dying from the condition each year.

Taken together, the studies found that people who felt stressed were 27 percent more likely later to be diagnosed with coronary heart disease, be hospitalized with the condition, or die from it.

Edmundson said the rise in heart disease risk related to stress is equivalent to smoking five cigarettes a day. However, there is no ironclad proof that stress is to blame for the heart problems.

One possible explanation is that stress raises the blood levels of hormones that can be take a toll on the heart.

In addition, people who are stressed might behave in ways that are less healthy, "like smoking, unhealthy dietary choices, physical inactivity etc. These mechanisms usually interact, making the situation much more complicated," said Dr. Demosthenes Panagiotakos, a professor at Harokopio University of Athens, who was not involved in the study.

In an email to Reuters Health, Panagiotakos said Edmundson's review supports the link between stress and heart disease, "however, this is based only on six relevant studies, a fact that makes the causal inference very difficult."

Edmundson said people can take steps to reduce their stress, such as exercise, yoga and meditation.

"Good old-fashioned exercise, good old-fashioned stress reduction techniques, are probably - the study hasn't been done yet - but are probably going to be good for healthy people to offset their risk of heart disease going forward," he said.

SOURCE: bit.ly/VNY5vj The American Journal of Cardiology, online September 12, 2012.

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