Findings of women's health initiative trial need not alarm users

Observational studies have suggested a major health benefit of postmenopausal hormone replacement therapy, including reductions in coronary heart disease, osteoporotic fractures, and colorectal cancer. Such studies have also suggested an increased risk for breast cancer and possibly stroke. Critics have said that the benefits, but not the risks, may simply reflect a healthy user bias and have demanded randomised trials. The women's health initiative is a randomised trial of these health outcomes to assess risks and benefits of intervention strategies in a postmenopausal population. The trial has shown harm for cardiovascular diseases, including coronary heart disease (the primary outcome) and stroke, although it showed benefits for hip fractures and bowel cancer. The relative risks for invasive breast cancer, coronary heart disease, and stroke were increased, although the absolute risks were very small. The findings may not be the same for types of hormone replacement therapy other than those used in this trial, or for lower doses of the regimen that was used—a point that is acknowledged by the authors of the study.

One treatment arm of the trial included over 16 000 postmenopausal women who were taking continuous combined oestrogen-progestogen hormone replacement therapy, using conjugated equine oestrogens 0.625 mg plus medroxyprogesterone acetate 2.5 mg daily, tested against placebo.1 This primary …