September 16, 2026
ByMaureen Salamon,
Executive Editor, Harvard Women’s Health Watch
- Reviewed byRobert H. Shmerling, MD,
Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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Use of estrogen-only hormone therapy by menopausal women may significantly lower their odds of developing Alzheimer’s-related brain changes or being diagnosed with dementia, according to a study published Sept. 8, 2026, in Neurology
Researchers analyzed two databases involving more than 20,000 women over age 50, comparing those who had reported estrogen-only hormone therapy use with women who didn’t use hormone therapy. (While the study didn’t explicitly state that the estrogen users had prior hysterectomies, estrogen-only therapy is advised only for women without a uterus. Progesterone is typically added to hormone therapy for women with a uterus to protect the uterus from changes in its lining that can lead to cancer.)
One database included 2,959 women whose brains were examined after death for typical features of Alzheimer’s disease, including the presence of amyloid protein. The other included 2,058 living women who had undergone cognitive testing, brain imaging, biomarker testing, or a combination of these tests
Estrogen-only users whose brains were examined after death were 35% less likely to show Alzheimer’s-related brain changes than non-users. In the other group, estrogen-only users had 39% lower odds than non-users of a dementia diagnosis during their lifetime and performed better on memory tests
The study was observational, meaning it can’t prove that estrogen therapy prevents dementia or Alzheimer’s-related brain changes. Since the analysis didn’t involve women who took combination estrogen-progesterone hormone therapy or used localized vaginal estrogen, the results also can’t be generalized to all hormone therapy users. The researchers also couldn’t assess whether the timing or length of treatment affected the findings because they lacked data on when women started hormone therapy or how long they used it. While the study provides some reassuring evidence that estrogen exposure may be helpful to women’s brains as they age, it isn’t a reason to start hormone therapy.
Image: © Yuichiro Chino/Getty Images
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