VANCOUVER, BC—Unopposed estrogen hormone replacement therapy (HRT) significantly increases the risks for ischemic strokes when compared to combination estrogen and progesterone HRT, even after it is discontinued, according to researchers at the 68th Annual AAN Meeting.

The researchers, led by Haseeb Rahman, MD, from Houston Methodist Hospital, Houston, TX, analyzed a total of 93,676 women aged 50–79 years old. Their data was retrieved from those who took part in the 12 ± 1 year Observational Study (OS) as part of the Women’s Health Initiative (WHI).

At baseline, 11,364 of the total participants had used unopposed estrogen while 58,461 had never used unopposed estrogen. A significantly greater proportion of those who used unopposed estrogen developed ischemic stroke outcomes (3.1%) compared with those who had never used unopposed estrogen (2.3%), (P<0.0001).

Similarly, yet not as significant, a greater proportion of those who had used EPT (7,993) at baseline developed ischemic stroke outcomes (2.8%), compared to those who never used EPT (2.4%) (P=0.09).

The long-term nature of this study reinforces previous study findings, that unopposed estrogen HRT increases risk for ischemic stroke, even after therapy is discontinued. However, the study suggests that that the continued combination of estrogen and progesterone HRT was not associated with a significantly increased risk. “Further prospective studies are required to further investigate these correlations,” concluded Dr. Rahman.