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August 19, 1998

Hormone Replacement Therapy and Heart Disease PreventionExperimentation Trumps Observation

Author Affiliations

From the Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena.

JAMA. 1998;280(7):650-652. doi:10.1001/jama.280.7.650

The true method of knowledge is experiment.—William Blake, 1788

Three different meta-analyses13 have concluded that estrogen replacement therapy (ERT) decreases the risk of coronary heart disease (CHD) by 35% to 50%. The predicted increase in life expectancy in hormone users, based on estimates of the risk of CHD in users of ERT derived from observational studies, is 2 to 3 years.2,4 The effects of ERT and combined estrogen-progestin replacement therapy (HRT) on lipids and fibrinolysis are strongly beneficial for both ERT and HRT.5 This has led to extrapolation of the results of observational studies of ERT to HRT and to promotion of the use of both ERT and HRT in women with CHD.2,6 The results of the Heart and Estrogen/progestin Replacement Study (HERS), which are reported by Hulley et al in this issue of JAMA,7 add critically important data on the effects of HRT. In this randomized controlled trial of 2763 postmenopausal women with established coronary disease, treatment with estrogen plus progestin did not reduce the rate of CHD events (eg, nonfatal myocardial infarction or CHD-related death). These findings are a sobering reminder of the limitations of observational research, the incompleteness of current understanding of the mechanisms of vascular disease, and the dangers of extrapolation.

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