Stanford Study Finds Estrogen Therapy Lowers Alzheimer's Risk in Postmenopausal Women
A comprehensive new study from Stanford University challenges previous beliefs that hormone therapy during menopause harms the brain and increases dementia risk. Published recently in the journal Neurology, the research found that women using estrogen-only menopausal hormone therapy (MHT) have a significantly reduced risk of developing the brain damage typical of Alzheimer's disease. Since estrogen-only therapy is usually prescribed to women without a uterus, most participants receiving this treatment had undergone hysterectomy.
The researchers uniquely analyzed postmortem brain tissue from 2,959 women, including 258 who took estrogen-only therapy and 2,701 who never used hormone therapy. They measured the density and distribution of amyloid plaques and neurofibrillary tangles, the pathological hallmarks of Alzheimer's. The study revealed a 35% lower risk of advanced Alzheimer's brain pathology among estrogen users. Additional findings included a 39% reduced risk of clinical dementia diagnosis and a 33% lower chance of memory decline and loss of functional independence.
Dr. Israel Yoles, a women's health expert at Clalit Health Services, explained that estrogen likely protects the brain by improving cerebral blood flow and reducing harmful plaques. Co-author Dr. Jennifer Bruno emphasized that while estrogen therapy's protective effect is modest compared to major risk factors like age or genetics, it is statistically significant and consistent. The study controlled for variables such as age, education, ethnicity, blood pressure, and genetic risk to confirm the hormone therapy's direct impact.
This research has major implications for over 30% of women who undergo hysterectomy by age 60 and are typically prescribed estrogen-only therapy. However, the results apply only to oral estrogen-only treatments; combined estrogen-progestin therapies and local hormone applications were not sufficiently studied. The authors note that starting hormone therapy during or near menopause maximizes benefits. The findings also contrast with the 2003 Women's Health Initiative study, which raised concerns about hormone therapy risks and led to a sharp decline in its use. In 2025, the FDA removed the strongest warning labels on hormone therapy, reflecting evolving evidence.
Dr. Bruno concluded that this new evidence directly contradicts previous medical advice against using hormone therapy to prevent memory decline, suggesting a reevaluation of treatment guidelines may be warranted.
