The Women's Health Initiative: Clinical Trials (WHI-CT)

Objectives:

To assess the safety and efficacy of three interventions on cardiovascular disease (CVD), cancer, and osteoporosis in postmenopausal women.

Background:

The clinical trial component of the WHI included three, overlapping randomized comparisons: hormone therapy, dietary modification, and calcium/vitamin D supplementation. The hormone therapy trial randomized womento one of two double-blinded trials: estrogen plus progestin or estrogen alone. The dietary modification trial evaluated the effect of a low-fat, high fruit, vegetable, and grain diet on preventing CVD and cancer. The calcium/vitamin D randomized women to either supplements or placebo. Women could have been randomized into one, two or all three trials.

Subjects:

A total of 68,132 women, aged 50-79 years were randomized into the three trials. The hormone therapy trial enrolled 16,608 women, 48,835 were randomized into the diet modification trial, and 36,282 were randomized into the calcium/vitamin D trial. Recruitment was carried out in 40 US clinical centers in 1993-1998.

Conclusions:

Overall health risks exceeded benefits from use of combined estrogen plus progestin after an average 5.2 year follow-up among healthy postmenopausal US women (JAMA 2002;288:321-333). Over approximately 8 years of follow-up, a low-fat dietary pattern did not reduce the risk of colorectal cancer (JAMA 2006;295:643-654). Calcium with vitamin D supplementation resulted in a small but significant improvement in hip bone density; however, no significant difference was observed in hip fractures (N Engl J Med 2006;354:669-683).