Estrogen-only hormone therapy and dementia risk: New link

What happened in the estrogen-only hormone therapy and dementia risk study

A study published in Neurology reported that later-life use of estrogen-only hormone therapy was associated with a lower risk of developing dementia and with biomarkers consistent with less Alzheimer’s-related pathology.

The researchers focused on estrogen-only therapy because earlier research has suggested estrogen-plus-progestin combination therapy may increase dementia risk, and they wanted to evaluate the estrogen-only pattern separately.

• Study publication: Neurology (2026)
• Key focus: estrogen-only hormone therapy used later in life
• Main outcome: dementia diagnosis and Alzheimer’s-related brain markers

What the evidence shows about estrogen-only hormone therapy and dementia risk

This was a retrospective analysis of medical records drawn from two large datasets, so it can show associations but cannot prove that estrogen-only hormone therapy prevents dementia.

Across both datasets, the study included 21,462 female participants who were followed for about three to five years starting at an average age of 71; 1,953 used hormone therapy and 19,509 did not, and those who used hormone therapy began after age 70 on average.

• Autopsy subgroup: 2,959 participants had autopsies after death at an average age of 82 to assess Alzheimer’s disease signs
• Biomarker/imaging subgroup: 728 participants completed brain scans or biomarker tests while living
• Clinical outcome: hormone therapy use was associated with 39% lower odds of receiving a clinical dementia diagnosis

Autopsy and biomarker findings tied to estrogen-only hormone therapy and dementia risk

In the autopsy dataset, people who had taken hormone therapy were less likely to show Alzheimer’s disease signs in the brain than those who had not taken hormone therapy.

After adjusting for age, education, genetics, race, and hypertension, hormone therapy users had 35% lower odds of signs of Alzheimer’s disease at autopsy compared with non-users.

• Composite autopsy score captured three hallmarks: amyloid-beta plaques, tau tangles, and neuritic plaques
• No signs at autopsy: 18% of hormone therapy users vs 10% of non-users
• All three signs present: 40% of hormone therapy users vs 51% of non-users
• Biomarkers: users had amyloid biomarker patterns in blood and spinal fluid consistent with less amyloid buildup in the brain (higher amyloid-beta levels suggesting less deposition as plaques)

Practical context for metabolic-health readers

For readers focused on metabolic health, the study’s adjustments included hypertension, a major vascular risk factor that can overlap with dementia risk, but the results still remained an association rather than proof of cause and effect.

The findings also sit alongside an important prescribing reality: in current standard practice, estrogen-only therapy is prescribed only for those who have had a hysterectomy because of endometrial cancer risk.

• The study examined hormone therapy use that typically began after age 70, which differs from current practice patterns
• If you already track cardiometabolic risks (like blood pressure), note that the study adjusted for hypertension when estimating odds of Alzheimer’s signs at autopsy

Limitations and why the results may not match today’s hormone therapy use

The authors emphasized that more research is needed before making recommendations about hormone therapy for brain health, and that the timing and type of hormone therapy use in this study differed from what is common today.

Study author Jennifer Bruno, Ph.D., of Stanford Medicine said the study looked back at women using hormone therapy decades ago, and that the results are informative but may not apply to current standards; she also noted that hormone therapy today is usually started in the late 40s to early 50s and stopped before age 60.

• The study does not prove hormone therapy prevents dementia; it shows an association
• Participants who used therapy started after age 70 on average, which differs from typical modern initiation and discontinuation ages
• Results are specific to estrogen-only therapy (not estrogen-plus-progestin)