Letters have been sent to all participants in the estrogen-alone study, 11,000 healthy postmenopausal women who have had a hysterectomy, informing them of a recent NIH review of the study data. After careful consideration of the data, NIH has concluded that with an average of nearly 7 years of follow-up completed, estrogen alone does not appear to affect (either increase or decrease) heart disease, a key question of the study. At the same time, estrogen alone appears to increase the risk of stroke and decrease the risk of hip fracture. It has not increased the risk of breast cancer during the time period of the study.
The increased risk of stroke in the estrogen-alone study is similar to what was found in the WHI study of estrogen plus progestin when that trial was stopped in July 2002. In that study, women taking estrogen plus progestin had 8 more strokes per year for every 10,000 women than those taking the placebo. The NIH believes that an increased risk of stroke is not acceptable in healthy women in a research study. This is especially true if estrogen alone does not affect (either increase or decrease) heart disease, as appears to be the case in the current study.
The NIH has determined that the results would not likely change if the estrogen trial continued to its planned completion in 2005. Furthermore, enough data have been obtained to assess the overall risks and benefits of the use of estrogen in this trial. WHI researchers have begun a detailed analysis of the data from the estrogen-alone study and expect to report full results in the next two months. The report, to be published in a peer-reviewed journal, will include additional data collected through the end of February 2004.
Contact: NHLBI Communications Office
NIH/National Heart, Lung, and Blood Institute