31-Country Study Finds Stable Angina More Common In Women Than Men

Main Category: Cardiovascular / Cardiology
Article Date: 25 Mar 2008 - 8:00 PST

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Although men have a higher rate of heart attacks, stable angina is 20 percent more prevalent in women, researchers reported in Circulation: Journal of the American Heart Association.

Researchers discovered the unexpected result in the first large-scale study investigating risk factors for stable angina. They pooled data from 74 studies involving 401,315 people living in 31 countries, including the United States. Of the studies' participants, 13,331 women and 11,511 men had stable angina.

"We were surprised to see this slight excess of angina in women, although it had been reported before in a few individual studies," said Harry Hemingway, M. D., lead author of the study. "What surprised us much more was its consistency. We found the same female excess across 31 countries, across four decades of studies, and across four decades of ages. It's hard to dismiss this as some artifact of study design."

A key implication of the study is that being male is not a risk factor for developing stable angina - contrary to the long accepted view of physicians. "In this study, men do not have more angina than women," said Hemingway, professor of clinical epidemiology at the University College London Medical School in England. "And that finding itself has implications for future research and patient care."

Angina is chest pain caused by myocardial ischemia, an inadequate supply of blood-borne oxygen to the heart muscle. Patients with stable angina experience pain after exercise or stress, which disappears when they rest. The causes of stable angina are less understood than the causes of heart attack. But since stable angina is commonly the first sign of symptomatic heart disease, it is important to find out what causes it.

The study follows a study Hemingway led in 2006 of stable angina patients diagnosed by physicians in Finland. In that study also, women showed a slightly higher incidence of the disorder than men.
"We were interested in pursuing the question of whether there was a sex difference in angina,"

Hemingway said. "We searched systematically the medical literature and found no large-scale studies of stable angina."

He and his U.S. and European colleagues wanted to avoid using studies in their analysis that relied on different diagnostic criteria. They selected 74 well-designed studies that included a proven, seven-item questionnaire, which provided them a standardized diagnosis of typical symptoms of stable angina.

The prevalence of the disorder varied widely among the 31 countries, from 0.73 percent to 14.4 percent in women, with an average of 6.7 percent. In men it varied from 0.76 percent to 15.1 percent, with an average of 5.7 percent.

The countries also differed significantly in their heart attack death rates, and in several areas that can influence the risk of heart disease. These included smoking rates, the attitudes of healthcare workers toward symptoms, and attitudes toward women.

However, when the team considered all factors, it found the higher angina rates persisted in women. Although the rates varied slightly from country to country, they were all significantly close to the meta-analysis' overall excess of 20 percent.

Even the known increased risk of cardiovascular disease in women after menopause made no difference in the analysis. The researchers found that pre- and postmenopausal women had statistically similar higher rates of stable angina.

"Our interpretation of the 74 studies is that stable angina is really not more common in men," Hemingway said. "The question is what are the underlying biological processes."

Compared to men, women develop angina more often in the small vessels of the heart than in the large coronary arteries. Physicians should reconsider how they view stable angina, Hemingway said. "If you think that narrowing of the large arteries is the only underlying cause, then that will color your judgment," he said. "Such narrowing is less common in women than in men. But a woman with typical angina symptoms may still have myocardial ischemia."

"If men had a choice in the angina they get, they would choose to get the type that women get," Hemingway said. "The symptoms are the same, but the risk of subsequent heart attack in women is lower."

The team's meta-analysis didn't investigate other causes of stable angina or the reason for excess in women.

Hemingway said future efforts should include more large epidemiologic studies involving thousands of stable angina patients to shed further light on the causes and consequences of angina, and how they differ between the sexes.

Co-authors are Claudia Langenberg, M.D.; Jacqueline Damant, M. Phil.; Chris Frost, Ph.D.; Kalevi Pyorala, M. D.; and Elizabeth Barrett-Connor, M.D.

Dr. Hemingway is supported by a public health career scientist award from the Department of Health.

Dr. Langenberg is supported by a Health of Public Ph.D. Fellowship from the Medical Research Council.

Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.

American Heart Association