Study Links Mental Stress and Coronary Disease

Mental stress brought on by math problems, reading aloud and, especially, speaking publicly about personal foibles can disrupt blood flow to the heart in people with coronary artery disease, a team of Los Angeles researchers reported today.

Their conclusions appear to confirm that mental stress plays a role in heart disease and perhaps heart attacks. The researchers also said their findings offer insight into the nation’s top killer and may eventually influence how some patients are advised to live.

“We can no longer look at patients only in terms of what physically stresses them,” said Dr. Alan Rozanski, a cardiologist at Cedars-Sinai Medical Center who headed the study. “We have to look at the totality of stresses in a patient who has heart disease.”

In the study, published today in the New England Journal of Medicine, the researchers subjected 39 men and women with coronary artery disease, as well as 12 healthy people, to a series of mentally challenging, frustrating or emotionally taxing tasks.

First they subtracted the number seven repeatedly from a four-digit number for five minutes. Then they took a deliberately confusing visual quiz. Later they read a prose passage aloud and gave a five-minute speech on their personal faults and unappealing habits.

The researchers monitored each person’s heart as he or she performed, looking for subtle changes indicating a reduction in blood supply to the heart. They compared those measurements to changes experienced as the subjects rode a stationary bicycle to exhaustion.

Fifty-nine percent of the patients with heart disease experienced abnormalities in heart function that indicated reduced blood flow, the researchers found. Only a small number of subjects without heart disease showed any change.

Thirty-six percent also experienced a more than 5% reduction in the amount of blood being expelled from the heart’s left ventricle. One patient experienced a 21% decrease. None of the people in the control group experienced any reduction.

The findings suggest a direct link between mental stress and a condition called ischemia--a temporary, often unnoticed reduction in blood supply to the heart. Prolonged or severe ischemia may in some cases foreshadow a heart attack.

However, Rozanski emphasized the need for further study before physicians can apply his team’s findings to treating heart patients. In the long run, he said, his work may contribute to a better understanding of the role of stressful situations in heart disease.

“We don’t specifically see anything that should alarm patients,” Rozanski said Wednesday in a telephone interview. “Physicians have . . . available means to evaluate each patient and can detect ischemia and use drugs to treat it.”

In the study, the largest and most frequent abnormalities in heart function came in response to publicly speaking about one’s shortcomings--though it is unclear whether the patients were reacting to anxiety, emotional arousal or both.

That observation suggests that personal and emotional stress is more powerful than purely cognitive stress such as that brought on by doing math or reading aloud, the researchers said. However, Rozanski emphasized that responses to stress were highly individual. Some people responded more strongly to doing math, for example.

The researchers found that the response to mental stress could be just as severe as the response to physical exercise. And in most of the subjects, the ischemia experienced was “silent”--that is, not associated with any chest pain or perceptible symptoms.

In an editorial accompanying Rozanski’s study, two Boston researchers who have done related work traced the reductions in blood flow to fat-clogged arteries. They said such arteries, instead of dilating in response to stress, inappropriately constrict. As a result, there is a reduction in blood supply.

According to Rozanski, director of cardiac rehabilitation at Cedars-Sinai, the link between mental stress and heart disease has long been suspected. Epidemiological studies of heart patients have also suggested a possible connection between heart attacks and mental stress.

Several years ago, advances in electrocardiogram technology allowed researchers to measure heart function while patients went about their daily lives. Those studies revealed that ischemia occurred often during the day and was not necessarily linked to physical exercise.

The Cedars-Sinai study carried that work a step further, exploring what types of events might be causing those changes. The researchers injected each subject with a small blood sample labeled with radioactivity, enabling them to take images of heart function.

But the study’s significance extends beyond the link to stress.

Rozanski said the research opens the door to further exploration of the mechanisms of ischemia and heart disease--for example, the effects on heart function of hormones released during periods of stress.

“If we could study this phenomenon and understand any mechanisms that may be operative, it would help us understand the pathophysiology of the disease,” he said of the link between mental stress and disease. “That leads to new therapies or better approaches to treatment.”