According to the American Heart Association, cardiovascular disease (CVD) remains the leading cause of death of women in America, with 44.6% of all female deaths occurring from CVD. It is estimated that one in two women will eventually die of heart disease or stroke , compared with one in 25 who will eventually die of breast cancer .

Most sudden deaths in women from CVD occur in those with no previous symptoms. Identifying women who are at increased risk and who may benefit from prevention, therefore, has the potential to reduce cardiovascular mortality in women. Several studies have found that certain measures of cardiovascular fitness (such as reduced exercise capacity) are associated with increased CVD mortality in healthy men. But it is not known if such tests can similarly foretell the course of disease in women.

A new study in the September 24, 2003 issue of the Journal of the American Medical Association (JAMA) investigated the role of exercise treadmill testing in predicting cardiovascular and all-cause death in a group of asymptomatic women. The results indicate that exercise testing does appear to predict mortality risk.

About the Study

The researchers enrolled 2,994 asymptomatic women, without known CVD, between 1972 and 1976. These women, aged 30 to 80 years at the time of enrollment, were followed annually through December 31, 1995, or until death. Women were ineligible if they were pregnant, had known CVD, or were deemed ineligible for exercise testing by the researchers.

At the time of enrollment, participants underwent exercise testing using a Bruce treadmill protocol (a standardized treadmill test for evaluating cardiovascular function).

The Findings

During an average follow-up of 20.3 years, there were 427 (14%) deaths from any cause, including 147 cardiovascular deaths (34% of all deaths). Women with high levels of exercise capacity (based on treadmill time) and high heart rate recovery (HRR, or the ability of the heart rate to return to normal after peak exercise) had significantly fewer all-cause and CVD deaths. Abnormal heart rhythms (ventricular arrhythmia) during exercise and failure to achieve target heart rate were associated with an increased risk of death.

The researchers also divided the study population into groups based on exercise capacity and HRR. They found that women who were below average were 3.5 times more likely to die of cardiovascular disease than who were women above average for both of these measures.

Moreover, after adjusting for age, the researchers discovered increases in risk of death (CVD and all-cause) associated with below average exercise capacity and HRR, inability to achieve target heart rate, and ventricular heart rhythm abnormalities were similar to the increases in risk from traditional risk factors like high blood pressure and cholesterol levels.

The study is limited, however, since the sample included few non-whites, which means that the study results may not apply to non-white women. In addition, the researchers only tested exercise capacity at baseline, when in fact this may have changed for many women (improved or worsened) over the course of follow-up.

How Does This Affect You?

Findings from this study support the potential use of exercise testing to determine which women may be at risk for CVD. In particular, exercise capacity and heart rate recovery are potentially powerful prognostic tools for both CVD and all-cause death. Before routinely recommending this type of screening, however, more research is needed to determine which asymptomatic women would benefit most from exercise testing.

Nevertheless, CVD remains the number one killer of women. Even without exercise testing, you can substantially reduce many of your risk factors for CVD by eating healthfully, not smoking, and getting plenty of exercise. And, even if you've already experienced heart disease or stroke, these and other lifestyle changes can help you successfully recover.