Estrogen-Only Hormone Therapy Linked to Lower Alzheimer’s Risk in Older Women
A new retrospective study of more than 21,000 women finds that use of estrogen-only menopausal hormone therapy is associated with reduced Alzheimer’s pathology, lower odds of dementia diagnosis, and fewer memory-related symptoms, though the findings apply mainly to women who have had a hysterectomy and may not generalize to all hormone users.
A recent longitudinal analysis of over 21,000 women suggests that estrogen-only menopausal hormone therapy (MHT) may confer a protective effect against Alzheimer’s disease. The study, led by Jennifer Bruno, PhD, of Stanford University, examined participants from the National Alzheimer’s Coordinating Center (NACC) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Women who reported oral estrogen-only use after age 50 showed lower odds of Alzheimer’s-related brain changes and dementia compared with non-users.
Study Design and Population
The researchers identified 1,953 women who used estrogen-only MHT and 19,509 who did not. All participants were aged 50 or older, and the cohort excluded users of topical estrogen. On average, women began hormone therapy after age 70 and were followed for three to six years.
Autopsy data were available for 258 MHT users and 2,701 non-users, with average age at death of 82 in both groups. The primary outcome was the NIA-AA Alzheimer’s Disease Neuropathologic Change (ABC) score, which integrates amyloid-beta deposits, Braak-stage tau tangles, and CERAD neuritic plaques.
Key Findings
| Outcome | Odds Ratio (OR) | 95% Confidence Interval | P-value |
|---|---|---|---|
| Increased Alzheimer’s pathology (autopsy) | 0.65 | 0.48-0.88 | 0.005 |
| Dementia diagnosis | 0.61 | 0.55-0.67 | <0.0001 |
| Memory or functional decline symptoms | 0.67 | 0.61-0.74 | <0.0001 |
| Amyloid pathology in plasma (β) | 0.44 | 0.16-0.73 | 0.0025 |
| Amyloid pathology in CSF (β) | 0.07 | 0.002-0.13 | 0.030 |
These results indicate that estrogen-only therapy was associated with a roughly 35-40 % reduction in the odds of Alzheimer’s pathology and a similar reduction in dementia and related symptoms. The authors described the effect as “modest but meaningful” and statistically significant.
Context and Controversy
Hormone replacement therapy has long been a contentious topic. Early observational work hinted at cognitive benefits, but the 2003 Women’s Health Initiative Memory Study (WHIMS) reported increased dementia risk with combined estrogen-plus-progestin formulations in women aged 65 and older. That trial also linked combined therapy to higher breast cancer and cardiovascular risks, prompting the FDA to issue black-box warnings that were later removed in 2022.
Consequently, MHT use among postmenopausal women fell from 26.9 % in 1999 to 4.7 % in 2020.
Simone Salemme, MD, of the University of Modena and Reggio Emilia, emphasized that MHT is not a single exposure; timing, regimen, route, and patient characteristics all influence outcomes. He called for research that follows women across the menopause-to-dementia life course, integrates biomarkers and neuropathology, and captures detailed exposure histories.
Limitations and Generalizability
The authors cautioned that their findings are most directly applicable to women who have undergone hysterectomy and therefore receive unopposed estrogen. CDC data suggest that about 35 % of women aged 65-74 have had a hysterectomy, limiting broader applicability. Moreover, participants in the study started therapy later in life than current clinical practice, which typically begins in the late 40s to early 50s and ends before age 60.
The observational design also leaves room for unmeasured confounding factors.
Implications for Practice
Despite these constraints, the study adds to a growing body of evidence that estrogen-only therapy, when used later in life, may support brain health and reduce Alzheimer’s risk. Bruno noted that the results challenge the longstanding recommendation against using MHT for memory preservation. However, clinicians should weigh individual patient histories, including surgical status and cardiovascular risk, before considering estrogen-only therapy as a preventive strategy for cognitive decline.
Future Directions
The editorial accompanying the study calls for a biologically ambitious and clinically grounded research agenda. Future investigations should aim to clarify “for whom, when, and under what conditions” MHT influences later-life brain health, incorporating diverse populations and detailed exposure data. Until such data are available, the protective association observed in this cohort should be interpreted with caution, acknowledging both its potential promise and its current limitations.
Source: MedPage Today