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Largest women's health prevention study ever – Women's Health Initiative

Some of the most common diseases that affect women after menopause are cardiovascular disease (the leading cause of death among U.S. women1), breast cancer (the second-leading cause of cancer deaths in U.S. women2), colorectal cancer (the third-leading cause of cancer death among U.S. women3), and osteoporosis (the leading cause of bone fracture in U.S. women4).

In 1991, the National Heart, Lung, and Blood Institute, part of NIH, launched the Women's Health Initiative (WHI) to understand better how these diseases affect post-menopausal women and to reduce the number of women who develop and die from these diseases. More than 160,000 post-menopausal women ages 50 to 79 participated in the 15-year study, making it one of the largest prevention studies involving women in the United States.5

WHI results in 2002 found that post-menopausal women taking combination (estrogen and progestin) hormone therapy for menopause symptoms had an increased risk for breast cancer, heart disease, stroke, blood clots, and urinary incontinence. Although women using combined hormone therapy had a lower risk of fractures and colorectal cancer, these benefits did not outweigh the risks. As a result, many women stopped taking hormone therapy, reducing their risk for breast cancer. One of the most important outcomes of the WHI was the sharp decline in breast cancer in 2003 after the WHI results were released in 2002.6 Today, the FDA urges women who take hormone therapy to take the lowest helpful dose for the shortest amount of time.7


  1. CDC, Leading Causes of Death in Females United States, 2010 (current listing)
  2. NIH, NCI, A Snapshot of Breast Cancer
  3. NIH, NCI, A Snapshot of Colorectal Cancer
  4. MedlinePlus, Osteoporosis - overview
  5. NIH, NHLBI, WHI Background and Overview
  6. NIH, NCI, Decrease in Breast Cancer Rates Related to Reduction in Use of Hormone Replacement Therapy
  7. FDA, Menopause and Hormones: Common Questions