Data from a new study published in the journal Neurology indicates that the use of estrogen-only hormone therapy in older age is associated with a reduced risk of developing dementia.
Scientists at Stanford Medicine analyzed the medical records of 21,462 women. Some of the participants underwent brain imaging and biomarker testing during their lifetime, while others underwent post-mortem autopsies (at an average age of 82) to evaluate signs of Alzheimer’s disease.
The study showed that women who received estrogen-only therapy were 35% less likely at autopsy to show neuropathological changes characteristic of Alzheimer’s (beta-amyloid plaques and tau protein tangles) compared to those who did not receive therapy. Furthermore, in living patients, biomarkers in blood and cerebrospinal fluid indicated lower amyloid accumulation in the brain. Overall, the use of hormone therapy was associated with a 39% lower likelihood of receiving a clinical diagnosis of dementia.
Notably, the researchers examined estrogen-only therapy—an approach primarily prescribed in modern practice following a hysterectomy to prevent the risk of endometrial cancer.
Despite these promising findings, the study’s authors urge caution. As lead author Jennifer Bruno explains, the data confirms only an association and does not prove direct causality. Additionally, women in the study started hormone therapy at an average age of 70, which differs sharply from current medical standards—today, therapy is typically initiated in the late 40s or early 50s and discontinued before age 60. Consequently, the researchers conclude that further studies aligned with modern standards are necessary before clinical recommendations regarding brain health can be modified.
