The HERS trial was the first study to put a damper on enthusiasm for hormone replacement therapy (HRT) as a preventive therapy for heart disease. A second trial called ERA (Estrogen Replacement and Atherosclerosis trial), reported at the 49th Annual Meeting of the American College of Cardiology, held in Anaheim, California, March 12-15, 2000, provides additional evidence that HRT does not prevent heart disease. The study implies that women with existing heart disease should not take HRT with the goal of preventing the advancement of their heart condition. ERA also suggests that women and their physicians should rely on medications already proven to prevent heart disease, such as cholesterol-lowering drugs like the statins, which have a dramatic effect on decreasing the risk of heart attacks and death.

"This study shows that HRT may not be as effective as we once thought in slowing heart disease," said David Herrington, MD, MDS, of Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina. He added that women and their doctors should make full use of therapies proven to prevent heart disease, such as the statins and other cholesterol-lowering drugs.

The ERA study included 309 older women, at an average age of 65-years-old, with heart disease who were randomly assigned to take Premarin® (estrogen), Prempro® (estrogen combined with a progestin), or a dummy pill (placebo). A sophisticated computerized technique called quantitative coronary angiography was used to measure any changes in their arteries due to treatment; the changes that were assessed included the build-up of cholesterol that causes narrowing of the arteries and can lead to chest pain and heart attack.

After a mean follow-up of 3.2 years, all three groups demonstrated the same rate of narrowing of the coronary vessels. Therefore, neither estrogen alone (Premarin®) nor estrogen combined with a progestin (Prempro®) changed the course of disease compared to no active treatment at all (placebo pill).

It should be emphasized that the women included in this study all had heart disease and were at a high risk for progression of heart disease when they entered the study. The average age of the women was 65 years. Approximately half of the women had already had a prior heart attack, about half had been treated with balloon angioplasty (another procedure used to open the clogged arteries), at least one quarter had diabetes, at least 60 percent had hypertension, about 18 percent were cigarette smokers, and more than 55 percent were overweight.

Dr. Herrington noted that the study was performed in older, less healthy women and therefore does not reflect what effects hormone therapy might have on preventing heart disease in younger, healthier women. However, the two studies done to date to assess the effects of HRT on the heart suggest that there is no protective effect against the advancement of heart disease. Younger, healthier women who wish to prevent heart disease are advised to eat a heart-healthy diet, exercise regularly, and not to smoke cigarettes.