Women who took estrogen-only menopausal hormone therapy showed fewer signs of Alzheimer’s disease in their brains and were less likely to be diagnosed with dementia, according to a large new study — though researchers stress it shows an association, not cause and effect.
Conducted at Stanford Medicine and published August 12, 2026 in Neurology, the study analyzed data from 21,462 women, including thousands who had brain scans, biomarker tests or autopsies (average autopsy age 82). Compared with non-users, women who used hormone therapy had 39% lower odds of a dementia diagnosis and 35% lower odds of Alzheimer’s-related brain pathology at autopsy. Notably, 18% of therapy users showed no Alzheimer’s signs at autopsy versus 10% of non-users, and their brains had less amyloid buildup.
An important detail
The benefit was seen specifically with estrogen-only therapy (not estrogen combined with progestin), which is prescribed to women who have had a hysterectomy. The analysis looked at amyloid plaques, tau tangles and neuritic plaques — the hallmarks of Alzheimer’s.
Read it carefully
“The results show an association and do not demonstrate that hormone therapy can prevent dementia,” cautioned study author Jennifer Bruno. Importantly, this historical group started therapy later (around age 70) than is typical today (late 40s to early 50s), so the findings may not translate directly to current practice. Hormone therapy has its own risks and benefits — a decision for each woman and her doctor, not something to start based on this study alone.
This article summarizes an observational study and is not medical advice. Do not start or stop hormone therapy without consulting your healthcare provider.