Effects of Estrogen Plus Progestin on Risk of Fracture and Bone Mineral Density
The Women's Health Initiative Randomized Trial
- Jane A. Cauley, DrPH;
- John Robbins, MD;
- Zhao Chen, PhD;
- Steven R. Cummings, MD;
- Rebecca D. Jackson, MD;
- Andrea Z. LaCroix, PhD, MPH;
- Meryl LeBoff, MD;
- Cora E. Lewis, MD, MSPH;
- Joan McGowan, PhD;
- Joan Neuner, MD, MPH;
- Mary Pettinger, MS;
- Marcia L. Stefanick, PhD;
- Jean Wactawski-Wende, PhD;
- Nelson B. Watts, MD;
- for the Women's Health Initiative Investigators
- Author Affiliations: Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pa (Dr Cauley); Department of Internal Medicine, University of California, Davis, School of Medicine, Sacramento (Dr Robbins); Division of Epidemiology and Biostatistics, Mel and Enid Zuckerman Arizona College of Public Health, University of Arizona, Tucson (Dr Chen); Research Institute at California Pacific Medical Center and Department of Epidemiology, University of California, San Francisco (Dr Cummings); Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, Ohio State University, Columbus (Dr Jackson); Women's Health Initiative Clinical Coordinating Center, Fred Hutchinson Cancer Research Center, Seattle, Wash (Dr LaCroix and Ms Pettinger), Endocrine-Hypertension Division, Brigham and Women's Hospital, Boston, Mass (Dr LeBoff); Division of Preventive Medicine, University of Alabama at Birmingham (Dr Lewis); National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, Md (Dr McGowan); Department of Medicine and Center for Patient Care and Outcomes Research, Medical College of Wisconsin, Milwaukee (Dr Neuner); Stanford Center for Research in Disease Prevention, Department of Medicine, Stanford University, Palo Alto, Calif (Dr Stefanick); University at Buffalo, State University of New York, Buffalo (Dr Wactawski-Wende); and University of Cincinnati College of Medicine, Cincinnati, Ohio (Dr Watts).
Abstract
Context In the Women's Health Initiative trial of estrogen-plus-progestin therapy, women assigned to active treatment had fewer fractures.
Objective To test the hypothesis that the relative risk reduction of estrogen plus progestin on fractures differs according to risk factors for fractures.
Design, Setting, and Participants Randomized controlled trial (September 1993-July 2002) in which 16 608 postmenopausal women aged 50 to 79 years with an intact uterus at baseline were recruited at 40 US clinical centers and followed up for an average of 5.6 years.
Intervention Women were randomly assigned to receive conjugated equine estrogen, 0.625 mg/d, plus medroxyprogesterone acetate, 2.5 mg/d, in 1 tablet (n = 8506) or placebo (n = 8102).
Main Outcome Measures All confirmed osteoporotic fracture events that occurred from enrollment to discontinuation of the trial (July 7, 2002); bone mineral density (BMD), measured in a subset of women (n = 1024) at baseline and years 1 and 3; and a global index, developed to summarize the balance of risks and benefits to test whether the risk-benefit profile differed across tertiles of fracture risk.
Results Seven hundred thirty-three women (8.6%) in the estrogen-plus-progestin group and 896 women (11.1%) in the placebo group experienced a fracture (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.69-0.83). The effect did not differ in women stratified by age, body mass index, smoking status, history of falls, personal and family history of fracture, total calcium intake, past use of hormone therapy, BMD, or summary fracture risk score. Total hip BMD increased 3.7% after 3 years of treatment with estrogen plus progestin compared with 0.14% in the placebo group (P<.001). The HR for the global index was similar across tertiles of the fracture risk scale (lowest fracture risk tertile, HR, 1.20; 95% CI, 0.93-1.58; middle tertile, HR, 1.23; 95% CI, 1.04-1.46; highest tertile, HR, 1.03; 95% CI, 0.88-1.24) (P for interaction = .54).
Conclusions This study demonstrates that estrogen plus progestin increases BMD and reduces the risk of fracture in healthy postmenopausal women. The decreased risk of fracture attributed to estrogen plus progestin appeared to be present in all subgroups of women examined. When considering the effects of hormone therapy on other important disease outcomes in a global model, there was no net benefit, even in women considered to be at high risk of fracture.
