Increased risk for ” Stroke (fatal and non-fatal) 12 cases more (44 cases in those on estrogen alone and 32 in those on placebo) Venous thrombosis(blood clot, usuallyin one of the deep veins of the legs) 6 cases more (21 cases in those on estrogen alone and 15 in those on placebo) (An increased risk of pulmonary embolism ” blood clots in the lungs ” was not statistically significant ” there were 13 cases in those on estrogen alone and 10 in those on placebo.) No difference in risk or uncertain effect for ” Coronary heart disease No significant difference in risk (neither increased nor decreased) ” 5 fewer cases (49 cases in those on estrogen alone and 54 in those on placebo). During the first two years of use, risk was slightly increased for estrogen alone, but it appeared to diminish over time. Colorectal cancer or total cancer No significant difference in risk (neither increased nor decreased) ” 1 more case for colorectal cancer and 7 fewer cases for total cancer (for colorectal cancer, 17 cases in those on estrogen alone and 16 in those on placebo; for total cancer, 103 cases in those on estrogen alone and 110 in those placebo) All deaths or those for a specific cause No significant difference in risk (neither increased nor decreased) ” 3 more deaths (for all deaths, 81 in those on estrogen alone and 78 in those on placebo) Breast cancer Uncertain effect ” 7 fewer cases (26 cases in those on estrogen alone and 33 in those on placebo). This finding was not statistically significant. Increased benefit for ” Bone fractures 6 fewer hip fractures (11 cases in those on estrogen alone and 17 cases in those on placebo)
The results above were not affected by race or ethnicity, or body mass index (BMI).
Another WHI hormone study, the estrogen-plus-progestin trial, was also stopped early. It was halted in July 2002 after 5.6 years of followup because of an increased risk of breast cancer and because the increased risks of breast cancer, coronary heart disease, stroke, and blood clots outweighed the benefits of a reduced risk of hip fracture and colorectal cancer.
The combined hormone therapy study involved 16, 608 participants, who were randomly assigned to receive either a daily intake of 0.625 mg of conjugated equine estrogens plus 2.5 mg of medroxyprogesterone (Prempro?„?), or a placebo. Combination therapy is used when women have a uterus to prevent the development of endometrial cancer.
Key findings of estrogen plus progestin compared to the placebo for every 10,000 women each year were: more strokes (8 more cases); an increased risk of breast cancer (8 more breast cancers); an increase in heart attacks (7 more heart attacks); a higher risk of blood clots (8 more women with blood clots in the lungs and 18 more with blood clots in the legs or lungs); a reduction in hip fractures (5 fewer hip fractures); and a drop in the risk of colorectal cancer (6 fewer colorectal cancers).
Rossouw cautioned that the findings for the two hormone therapy studies should not be compared directly. "At baseline, the women in the estrogen-alone study had a higher risk of cardiovascular disease than those in the estrogen-plus-progestin trial. Those in the estrogen-alone study were more likely to have such heart disease risk factors as high blood pressure, high blood cholesterol, diabetes, and obesity."
Women in both hormone trials are now in a followup phase, due to last until 2007, during which their health will be closely monitored.
WHI was launched in 1991 and consists of a set of clinical trials to test the preventive effects of postmenopausal hormone therapy, diet modification, and calcium and vitamin D supplements on heart disease, fractures, breast and colorectal cancer, as well as an observational study, which is looking for predictors and biological markers for disease. The diet modification trial involves nearly 49,000 women, the calcium/vitamin D trial about 36,000 women, and the observational study about 94,000 women ” all three studies are continuing.
NHLBI collaborates on the WHI with the National Cancer Institute, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the National Institute on Aging, and the Office of Research on Women's Health, all parts of the NIH.
To arrange an interview about the WHI, call the NHLBI Communications Office at (301) 496-4236.
Additional information on menopausal hormone therapy, including the WHI estrogen-plus-progestin study, can be found on the NIH Website at www.nih, on the NHLBI Website at www.nhlbi.nih, and on the FDA Website at www.fda.