Women taking estrogen-only hormone therapy showed fewer Alzheimer's signs in brain tissue

A study published in Neurology on August 12, 2026, found that women using estrogen-only hormone therapy later in life had 35% lower odds of showing Alzheimer's signs at autopsy and 39% lower odds of a clinical dementia diagnosis. Led by Jennifer Bruno of Stanford Medicine, the research analyzed data from over 21,000 women. However, the study's subjects started therapy at an average age of 70, which differs from current medical standards of starting in the late 40s to early 50s.

Estrogen-only hormone therapy

• ▪Under current medical practice, estrogen-only hormone therapy is prescribed only to individuals who have undergone a hysterectomy due to the risk of endometrial cancer.
• ▪Earlier studies suggested that hormone treatments combining estrogen with progestin may raise the risk of developing dementia.
• ▪A study published in Neurology on August 12, 2026, analyzed medical data from 21,462 female participants, of whom 1,953 used estrogen-only hormone therapy and 19,509 did not.

Dementia risk reduction

• ▪Women in the study published in Neurology on August 12, 2026, who used estrogen-only hormone therapy were less likely to show memory problems or declines in everyday functions.
• ▪Estrogen-only hormone therapy use was associated with 39% lower odds of receiving a clinical dementia diagnosis, according to the study published in Neurology on August 12, 2026.

Alzheimer's autopsy findings

• ▪Among study participants whose brains were examined after death, 18% of estrogen-only hormone therapy users showed no signs of Alzheimer's disease at autopsy, compared to 10% of non-users.
• ▪After accounting for factors like age, education, genetics, race, and hypertension, estrogen-only hormone therapy use was associated with 35% lower odds of showing signs of Alzheimer's disease at autopsy.
• ▪At autopsy, 40% of estrogen-only hormone therapy users showed all three major signs of Alzheimer's disease, compared to 51% of women who did not use the therapy.

Amyloid biomarker levels

• ▪Higher levels of amyloid-beta protein in blood and spinal fluid can indicate that less of the protein is being deposited in the brain as plaques.
• ▪Biomarker tests collected during life showed that women using estrogen-only hormone therapy had amyloid biomarker levels in blood and spinal fluid consistent with less amyloid accumulating in the brain.

Study timing limitations

• ▪Participants in the study began estrogen-only hormone therapy at an average age of 70, whereas current standard practice generally starts therapy in the late 40s to early 50s and stops before age 60.
• ▪Study author Jennifer Bruno of Stanford Medicine emphasized that the findings show an association and do not demonstrate that hormone therapy can prevent dementia.

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