There's more bad news about hormone replacement therapy this week. On the heels of estrogen being named a carcinogen by the US government, twenty years of prospective follow-up in the Nurses' Health Study show that daily estrogen doses of 0.625 mg or higher plus progestin may increase the risk of stroke by up to 45%, according to a report in the December 19th issue of the Annals of Internal Medicine.
Dr. Francine Grodstein, of the Channing Laboratory, in Boston, and associates evaluated completed questionnaires and medical records for 70,533 postmenopausal women. Between 1976 and 1996, a total of 1258 major coronary events and 767 strokes were identified in the cohort.
Dr. Grodstein's group found that that the age-adjusted relative risk of a major coronary event was 0.54 for current users of hormone replacement therapy (HRT) compared with women who never used HRT.
While they observed little overall difference in the relative risk of stroke among users and non-users of HRT, stroke risk varied by daily estrogen dose. Stroke risk was lower among women who received estrogen at 0.3 mg/d compared who those who took 0.625 or 1.25 mg/d. And among women taking 0.625 mg/d of estrogen combined with progestin, the authors observed a 45% higher risk of stroke compared with those who never took HRT.
In an accompanying editorial, Drs. Deborah Grady and Stephen B. Hulley, of the University of California at San Francisco, suggest that "hormone therapy may have mixed effects, causing thrombotic events while improving the lipoprotein profile." If that is the case, they speculate that prothrombotic activity may be more damaging to the small vessels of the cerebrovascular circulation than to the larger vessels of the coronary circulation.