Women's Health Initiative (WHI)

Understanding Menopause > Women's Health Initiative (WHI)

Timeframe of studies: 1993-1998
Number of Participants: 161,808
Average age of women at enrollment: 63
Percentage of minority women: 17.5

WHI focused on defining the risks and benefits of strategies that could potentially reduce the incidence of heart disease, breast and colorectal cancer, and fractures in postmenopausal women. Between 1993 and 1998, the WHI enrolled postmenopausal women in the age range of 50-79 years into a set of clinical trials (trials of low-fat dietary pattern, calcium and vitamin D supplementation, and 2 trials of postmenopausal hormone use) and an observational study at 40 clinical centers in the United States.

The effect of hormones on overall health was an important consideration in the design the clinical trial. The hormone trial had two studies: the estrogen-plus-progestin study of women with a uterus and the estrogen-alone study of women without a uterus. In both hormone therapy studies, women were randomly assigned to either the hormone medication being studied or to a placebo. These studies have now ended. The women in these studies are now participating in a follow-up phase, which will last until 2010.

In the estrogen plus progestin trial, the participants had increases in coronary heart disease, stroke, and pulmonary embolism, compared to women taking placebo pills. There were benefits of estrogen plus progestin, including fewer cases of hip fractures and colon cancer, but on balance, the harm was greater than the benefit. The study, which was scheduled to run until 2005, was stopped after an average follow-up of 5.2 years.

In the estrogen alone trial, women with prior hysterectomies were assigned to daily estrogens (Premarin) or a placebo pill. This study was also stopped ahead of schedule in February 2004 by the National Institutes of Health because of increased stroke risk. During 7.1 years of follow up, estrogen provided no overall protection against heart attack or coronary death in healthy postmenopausal women.

Current as of June 2007