About 5 percent of women considered low-risk for heart disease by current classification standards have evidence of advanced coronary artery calcium and may be at increased risk for cardiovascular events, according to a report in the Dec. 10/24 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
The Framingham risk score—which includes such factors as age, cholesterol and blood pressure levels, smoking habits and diabetes—is a standard approach for assessing an individual's risk of developing coronary heart disease in the next 10 years, according to background information in the article. Americans are considered low-risk if they have an estimated risk of less than 10 percent in 10 years, and high risk is 20 percent or greater in 10 years. Approximately 95 percent of U.S. women younger than 70 are considered low-risk and therefore do not qualify for aggressive management of risk factors. "Nevertheless, most women will ultimately die of heart disease, suggesting that the Framingham risk score alone does not adequately stratify women in ways that would be useful for targeted preventive interventions," the authors write.
Susan G. Lakoski, M.D., M.S., of the Wake Forest School of Medicine, Winston-Salem, N.C., and colleagues assessed 3,601 women age 45 to 84 when the study began, in 2000. Computed tomographic (CT) scans of the chest were used to determine scores for coronary artery calcium. High scores indicate a significant amount of calcium deposits, which has previously been associated with heart disease risk but is not included in the Framingham risk score. Medical history, measurements and laboratory tests were also taken at the beginning of the study, and participants were interviewed by telephone every nine to 12 months about subsequent cardiovascular diagnoses and hospital admissions.
A total of 2,684 (90 percent) of the women were considered low-risk based on the Framingham risk score. About one-third (32 percent) of them had detectable calcium in their coronary arteries. Over an average of 3.75 years, 24 of the low-risk women had heart events (such as heart attack and heart pain)—a 0.9 percent risk—and 34 (a 1.3 percent risk) had a cardiovascular disease event, including heart events, stroke or death.
"Compared with women with no detectable coronary artery calcium, low-risk women with a coronary artery calcium score greater than zero were at increased risk for coronary heart disease and cardiovascular disease events," the authors write. In addition, almost 5 percent of the low-risk women had advanced coronary artery calcium, defined as a score of 300 or greater. These women had a 6.7 percent risk of a heart event and 8.6 percent risk of a cardiovascular event over the 3.75-year follow-up.
"These data shed new light on cardiovascular disease risk and the modalities to evaluate and treat middle-aged and older women," the authors write. "This study also provides novel data in support of the 2007 guidelines on cardiovascular disease prevention in women, suggesting that women with coronary artery calcium are at potentially higher risk than a Framingham risk score classification would suggest." Studies with longer-follow up periods will be required to determine which low-risk women should be screened for coronary artery calcium or treated more aggressively for heart disease risk factors, they conclude.