Harvard Women's Health Watch

Women's Health Initiative: Not over yet

The largest study of women's health has raised at least as many questions as it has answered. Stay tuned.

In December 1993, the federally funded Women's Health Initiative (WHI) set out to enroll one out of every 200 women in the United States, ages 50–79, in a 12-year study to fill gaps in medical knowledge about postmenopausal women's health and chronic disease prevention. This prodigious undertaking involved 40 clinical centers, 1,000 investigators and staff, and 161,808 women — the largest study of its kind and the most comprehensive look to date at several women's health problems.

The goal was daunting: to find out if hormone therapy, a low-fat diet, and calcium supplements reduced the risk for major diseases affecting older women, including cardiovascular disease (heart attack and stroke), breast cancer, colon cancer, and osteoporosis. The WHI's ambitious aims reflected the somewhat limited state of knowledge about women's health at the time. Much was assumed, but little had been tested — and a "one size fits all" approach predominated. For example, many clinicians routinely prescribed estrogen with or without a progestin to women after menopause, even though the practice had never been proved safe or effective. The same was true for advice about a low-fat diet to prevent breast cancer and calcium supplements to protect bones.

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