Hormone therapy and the risk of stroke: perspectives 10 years after the Women's Health Initiative trials

Principal findings on stroke from the Women's Health Initiative (WHI) clinical trials of hormone therapy indicate that estrogen, alone or with a progestogen, increases a woman's risk of stroke. These results were not unexpected, and research during the past decade has tended to support these findings. Consistent evidence from clinical trials and observational research indicates that standard-dose hormone therapy increases stroke risk for postmenopausal women by about one-third; increased risk may be limited to ischemic stroke. Risk is not modified by age of hormone initiation or use, or by temporal proximity to menopause, and risk is similar for estrogen plus progestogen and for unopposed estrogen. Limited evidence implies that lower doses of transdermal estradiol (<= 50 mu g/day) may not alter stroke risk. For women less than 60 years of age, the absolute risk of stroke from standard-dose hormone therapy is rare, about two additional strokes per 10 000 person-years of use; the absolute risk is considerably greater for older women. Other hormonally active compounds - including raloxifene, tamoxifen, and tibolone - can also affect stroke risk.