Women who used estrogen-only hormone therapy later in life were less likely to develop dementia and showed fewer signs of Alzheimer's disease in their brains, according to a large study of more than 21,000 participants. The findings were published August 12, 2026, in Neurology, the medical journal of the American Academy of Neurology.
The research
Researchers analyzed medical data from two large datasets, including 21,462 female participants. In one dataset, 728 participants received brain scans or biomarker testing during life; in the other, 2,959 underwent autopsies after death (average age 82) to look for Alzheimer's evidence. Participants were followed for about 3–5 years, starting at average age 71. Among all, 1,953 used hormone therapy (estrogen-only) and 19,509 did not. On average, hormone therapy users began after age 70.
The study found that hormone therapy use was linked to 39% lower odds of a clinical dementia diagnosis. At autopsy, 18% of hormone therapy users showed no Alzheimer's signs, compared to 10% of non-users. Conversely, 40% of users showed all three key Alzheimer's features (amyloid plaques, tau tangles, neuritic plaques), versus 51% of non-users. After adjusting for age, education, genetics, race, and hypertension, hormone therapy was associated with 35% lower odds of Alzheimer's brain changes.
Biomarker tests (blood and spinal fluid) also suggested less amyloid buildup in hormone therapy users, as higher levels of amyloid-beta in blood/fluid indicate less is deposited in the brain as plaques.
Lead author Jennifer Bruno, PhD, of Stanford Medicine, cautioned: "While these findings help us better understand the relationship between hormone therapy use and various markers of dementia, more research needs to be done before we can make recommendations to women about their use of these therapies in relation to their brain health." She noted that the women used hormone therapy decades ago, with timing and type differing from current practice, so results may not apply today.
Why it matters
This study adds to growing evidence that estrogen may play a protective role in brain aging. For women considering hormone therapy for menopause symptoms, these findings suggest potential cognitive benefits, though the association does not prove causation. Current U.S. guidelines recommend hormone therapy at the lowest effective dose for the shortest duration, primarily for symptom relief, and estrogen-only is prescribed only for women without a uterus. The study's large sample and autopsy data strengthen the evidence, but more research is needed to clarify how timing, type, and duration affect brain health.
What you can do
If you're a woman exploring hormone therapy, discuss the risks and benefits with your doctor, considering your personal and family brain health history. Regardless, adopting a brain-healthy lifestyle—regular exercise, a Mediterranean diet, quality sleep, and mental stimulation—can support cognitive resilience. Stay tuned for more research on this topic.
Source: ScienceDaily Mind & Brain
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