The Heart and Estrogen / Progestin Replacement Study (known as “HERS”) was a randomized clinical trial to determine the long-term effect of estrogen combined with progestin on older post-menopausal women with coronary heart disease. HERS was conducted for 4.1 years and was followed with a subsequent study known as HERS II for an additional 2.7 years. In total, the studies were conducted from 1993 to 2000 and involved 20 outpatient and community-based clinical centers across the United States. HERS had more than 2,700 women (average age = 67) participate. In HERS II, 2,300 of those the first study’s participants continued to be observed.
During the HERS study, women either received estrogen and progestin or a placebo. During HERS II, women were prescribed open-label hormone therapy according to the discretion of the patient’s physician.
Some of the important findings from the HERS II study included the following:
· The relative hazard for venous thromobembolism was measured among the groups over the course of both of the studies. The study results were startling – the women who received estrogen and progestin treatment for the 6.8 years had increased rates of thromobembolism and biliary tract surgery.
· The women who received the estrogen and progestin hormones were at a higher risk for coronary heart disease (CHD) events during the first year. This risk decreased over years 3 through 5.
· Women were no more protected from CHD by taking the estrogen and progestin therapy. In fact, although the women on the hormones had lower rates of CHD during the final years of HERS, this did not translate into a continued decreased risk over the course of the HERS II study.
· Researchers concluded after the HERS and HERS II studies that postmenopausal women should not use estrogen plus progestin therapy to reduce the risk for CHD.
· “Postmenopausal therapy with estrogen plus progestin increases risk for venous thrombeoembolism in women with coronary heart disease.