Hormone therapy linked to increased risk of stroke

Postmenopausal women taking hormone therapy appear to have an increased risk of stroke regardless of when they started treatment, according to a report in the April 28 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

“Many controversies remain regarding the risks and benefits of postmenopausal hormone therapy,” according to background information in the article. There have been previous studies analyzing the risk of stroke with use of hormone therapy, but these did not determine stroke risk for younger women taking hormone therapy near the onset of menopause.

Francine Grodstein and colleagues at Boston’s Brigham and Women’s Hospital (BWH) and Harvard Medical School evaluated stroke risk associated with hormone therapy in 121,700 women (age 30 to 55 at the beginning of the study) who participated in the Nurses’ Health Study from 1976 to 2004. There were 360 cases of stroke among women who had never used hormones and 414 cases of stroke among women who were currently using hormones.

Compared with women who had never used hormones, women currently taking hormone therapy had an increased risk for stroke (39 percent for those taking estrogen and 27 percent for those taking estrogen with progestin). “This increased risk was observed for women initiating hormone therapy at young ages or near menopause and at older ages or more than 10 years after menopause,” the authors write. Taking hormone therapy for less than five years at younger ages was not linked to a clear increase in stroke, possibly due to the small number of cases.

“The incidence of stroke was relatively low in younger women, and the attributable risk in women aged 50 through 54 years indicated approximately an additional two cases of stroke per 10,000 women per year taking hormones,” the authors write. They also observed a strong relationship between dose of estrogen and stroke, with larger doses increasing the risk.

“In summary, our findings in the Nurses’ Health Study indicate that hormone therapy is associated with an increased risk of stroke, regardless of the hormone regime or the timing of hormone therapy initiation,” the authors conclude. “However, in younger women, who are at lower absolute risk of stroke, the attributable risk of stroke owing to hormone use is modest, and our data suggest that risk might be further minimized by lower doses and shorter duration of treatment.”