HRT Can Significantly Increase Stroke RiskApr 30, 2008 | Parker Waichman LLP
A new study reveals that high doses of hormone replacement therapy (HRT) can increase post-menopausal women’s stroke risk regardless of when the HRT begins. While the risk for stroke seems to be lower in younger women taking HRT and in women taking the lowest doses of estrogen, Harvard researchers say women who took high hormone doses experienced an increased stroke risk by as much as 62 percent.
"If you take medium to higher doses of hormone therapy, you are at increased risk of stroke," said Dr. James Liu, chairman of the Department of Obstetrics and Gynecology at MacDonald Women's Hospital, University Hospitals Case Medical Center in Cleveland. "If you are on estrogen, the risks of clotting abnormalities are slightly increased versus if you are not on estrogen," Liu said. "So, the risk of stroke is increased." The report was published in the April 28 edition of the Archives of Internal Medicine.
Francine Grodstein and colleagues at Brigham and Women's Hospital and Harvard Medical School collected data on 121,700 women who participated in the Nurses' Health Study from 1976 to 2004. Researchers looked at the link between HRT and stroke and found that 360 women who had never used HRT had strokes compared with 414 women taking hormones. "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 researchers wrote.
Women taking HRT for less than five years and at younger ages did not have a clear increase of stroke. The researchers noted that this could have been because only a small number of cases were studied. "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 researchers added.
Liu noted that older women, in general, are at an increased risk of stroke due to their age, whether or not they are taking HRT. Also, higher estrogen doses were associated with an increased risk for stroke and women taking high estrogen doses increased their risk of stroke by 62 percent.
"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 researchers concluded. "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."
Earlier this month, another study—Dose-Response Effect of Estrogen on the Kidney and Heart—revealed that estrogen replacement therapy (ERT) may increase the risk of cardiovascular disease and found moderate and high doses of ERT increased problems in the kidney and heart, suggesting ERT dosage may be an important factor in a woman’s overall health.