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Use of hormone replacement therapy plummeted after publication of findings from the Women's Health Initiative trial

In the mid-1990s, an estimated 38 percent of postmenopausal women in the United States used estrogen plus progestin hormone therapy (EPT) or estrogen therapy alone (ET). On May 31, 2002, the Women's Health Initiative (WHI) study of hormone therapy (HT) in women with an intact uterus was stopped after an average of 5 years because the risks associated with the use of HT (breast cancer, coronary heart disease, and stroke) were found to outweigh the benefits.

By December 31, 2002, 5 months after the trial results were published (July 9, 2002), 46 percent fewer women were taking EPT compared with the average proportion of women using EPT 2 years before the results were published (a decline from 14.6 percent to 7.9 percent). ET use declined by 28 percent during the same period (from 12.6 percent to 9.1 percent).

These findings are from a study by the HMO Research Network Center for Education and Research on Therapeutics (CERT) and the HMO Cancer Research Network. The study was supported in part by the Agency for Healthcare Research and Quality through funding from its patient safety program to the CERTs initiative (HS11843). A multicenter research team used automated pharmacy data to identify all oral and transdermal estrogen and progestin dispensed to 169,586 women aged 40 to 80 years who were enrolled in five U.S. health maintenance organizations. The researchers examined EPT and ET use between September 1, 1999 and June 31, 2002 (baseline) and December 31, 2002 (followup).

Along with the decline in EPT use following published trial results, there was an immediate decrease in the proportion of women beginning EPT and ET, from 0.4 percent and 0.3 percent at baseline, respectively, to 0.2 percent for both groups at followup. A striking finding was the high discontinuation rates among ET users despite the fact that the ET portion of the WHI trial (for women who had undergone hysterectomies) was ongoing during the study period. The ET portion of the trial was stopped on March 4, 2004, due to increased stroke risk. It is unclear whether the discontinuation of ET reflected women's and providers' misunderstanding of the HT trial results or a generalization of the HT findings to ET, note the researchers.

See "Hormone therapy prescribing patterns in the United States," by Diana S.M. Buist, Ph.D., Katherine M. Newton, Ph.D., Diana L. Miglioretti, Ph.D., and others, in the November 2004 Obstetrics & Gynecology 104, pp. 1042-1050.

Editor's Note: Another AHRQ-supported study on a related topic found that the prevalence of hormone replacement therapy among Medicaid-insured women aged 50 and older in all racial groups also decreased significantly following release of the WHI study findings. For more details, see Hillman, J.J., Zuckerman, I.H., and Lee, E. (2004). "The impact of the Women's Health Initiative on hormone replacement therapy in a Medicaid program." (AHRQ grant HS11673). Journal of Women's Health 13(9), pp. 986- 992.

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