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Women's Health Initiative (WHI)

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ClinicalTrials.gov Identifier: NCT00000611
Recruitment Status : Completed
First Posted : October 28, 1999
Last Update Posted : April 15, 2016
Information provided by:

October 27, 1999
October 28, 1999
April 15, 2016
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March 2005   (Final data collection date for primary outcome measure)
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Complete list of historical versions of study NCT00000611 on ClinicalTrials.gov Archive Site
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Women's Health Initiative (WHI)
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To address cardiovascular disease, cancer, and osteoporosis, the most common causes of death, disability, and impaired quality of life in postmenopausal women. The three major components of the WHI are: a randomized controlled clinical trial of hormone replacement therapy (HRT), dietary modification (DM), and calcium/vitamin D supplementation (CaD); an observational study (OS); and a community prevention study (CPS). On October 1, 1997, administration of the WHI was transferred to the NHLBI where it is conducted as a consortium effort led by the NHLBI in cooperation with the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Cancer Institute (NCI), and the National Institute on Aging (NIA).


Prior to 1991, little research had focused on health issues unique to, or more common for, women. This was especially the case for studies of chronic diseases and their prevention in mature women. These conditions (coronary heart disease, cancer, and osteoporosis) are the leading causes of impairment of quality of life, morbidity, and mortality in post-menopausal United States women. The WHI, mandated by Congress, was established in 1991 by the National Institutes of Health and located in the Office of the Director (OD). The Clinical Coordinating Center for the clinical trial/observational study was funded in September 1992 and the 16 Vanguard Clinical Centers were funded in March 1993. The initial protocol was developed jointly by the Clinical Coordinating Center and the Program Office and was reviewed and approved by the Investigators Committee on April 20, 1993. Additional clinical centers were funded in 1994.

On October 1, 1997, administration of the WHI was transferred to the NHLBI where it is conducted as a consortium effort led by the NHLBI in cooperation with the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Cancer Institute (NCI), and the National Institute on Aging (NIA).


As has been described in the objective, the WHI has three major components: a randomized controlled clinical trial, an observational study, and a study of community approaches to developing healthful behaviors. Recruitment for the WHI began in September 1993 and ended in December 1998. Six clinical centers completed recruitment in January 1997. The remaining 34 centers completed recruitment in December 1998.


The clinical trial component consists of three subtrials: the hormone replacement trial, the dietary modification trial, and the calcium /vitamin D supplementation trial. Approximately 27,500 women aged 50 to 79 are participating in the HRT, which tests whether long-term HRT reduces coronary heart disease and fractures without increasing breast cancer risk. Women with a uterus were randomized to receive either estrogen plus progestin or a placebo. Progestin was added to protect women with a uterus from endometrial cancer. Women who have had a hysterectomy were randomized to receive either estrogen alone or a placebo. The estrogen plus progestin trial was stopped early on July 8, 2002 after an average follow-up of 5.2 years on the recommendation of the Data and Safety Monitoring Board. The estrogen alone study continued unchanged until March 2, 2004 when the NIH instructed participants to stop taking their study pills and to begin the follow-up phase of the study. . Participants in the estrogen alone study will be followed for eight to 12 years and have clinic visits every six months to assure safety and assess their health.

The dietary modification trial component studies the effect of a low-fat, high fruit, vegetable and grain diet on breast cancer, colorectal cancer and heart disease in 48,000 postmenopausal women. Participants are randomized to a comparison group which maintains usual dietary habits or to a dietary change group. Women in the dietary change group decrease their fat intake to 20 percent of total daily calories, increase fruit and vegetable consumption to five or more servings per day, and increase grains to six or more servings per day. Additionally, they monitor their food intake and attend nutrition group meetings to learn more about changing their diets in the first year. Thereafter they attend four meetings per year.

The calcium/vitamin D supplementation subtrial tests whether calcium and vitamin D supplements reduce the risk of hip and other fractures and colorectal cancer in postmenopausal women. Women in the hormone replacement therapy and the dietary modification trials are encouraged to join the calcium/vitamin D supplementation study. Approximately 45,000 postmenopausal women are randomized into one of two study groups. One group was randomly assigned to receive 1,000 mg of elemental calcium (as calcium carbonate) and 400 International Units of vitamin D₃daily. The second group received a matching placebo.

Women already taking calcium supplements can continue to take them. Participants will be followed for eight to 11 years and contacted by their clinical center every six months to assure their safety and assess their health.

Total number of trial participants in all three subtrials is 68,135.


The several goals of the study include: to give reliable estimates of extent to which known risk factors predict heart disease, cancers, and fractures; to identify new risk factors for these and other diseases in women; to compare risk factors, presence of disease at the start of the study and new occurrences of disease during the WHI in all study components; and to create a future resource to identify biological indicators of disease, especially substances and factors found in blood. The study enrolled 93,726 postmenopausal women and will track them for an average of nine years. Participants fill out periodic health forms and visit the clinic three years after enrollment. They take no medication and do not change their health habits.


The community prevention study consists of 12 separate studies conducted at eight of the Centers for Disease Control and Prevention's (CDC) University-based Prevention Research Centers through a cooperative agreement between NIH and CDC. The 12 studies began in October 1995 and continue for an additional five years. The collaboration supports health promotion and disease prevention research and demonstration projects that are community-based and focus on healthy behaviors that prevent the major causes of death and disability and that promote health practices that lead to more effective public health interventions. Each project provides research dissemination and translation of findings into community interventions. Topics under study include: attitudes towards hysterectomy, oophorectomy, and surgical menopause among African Americans; reducing cardiovascular disease risk among Black women; environmental and policy interventions to increase physical activity among minority women ages 40 to 75; peer support intervention for cardiovascular disease risk among African American women, aged 40 and older; assessing the effectiveness of a brief medical-provider educational intervention for osteoporosis in minority women aged 40 and older; improving the delivery of diabetes care to women in minority groups; and assessment of moderate physical activity among women.

Phase 3
Allocation: Randomized
Primary Purpose: Prevention
  • Bone Diseases
  • Breast Neoplasms
  • Cardiovascular Diseases
  • Colonic Neoplasms
  • Coronary Disease
  • Heart Diseases
  • Myocardial Ischemia
  • Osteoporosis
  • Postmenopause
  • Drug: hormone replacement therapy
  • Drug: estrogens
  • Drug: progestins
  • Drug: estrogen replacement therapy
  • Behavioral: diet, fat-restricted
  • Drug: calcium
  • Drug: vitamin D
  • Behavioral: dietary supplements
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*   Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
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March 2005   (Final data collection date for primary outcome measure)
Postmenopausal women ages 50 to 79.
Sexes Eligible for Study: Female
50 Years to 79 Years   (Adult, Senior)
Contact information is only displayed when the study is recruiting subjects
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National Heart, Lung, and Blood Institute (NHLBI)
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
  • National Cancer Institute (NCI)
  • National Institute on Aging (NIA)
Investigator: Ross Prentice Fred Hutchinson Cancer Research Center
National Heart, Lung, and Blood Institute (NHLBI)
January 2006

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP