Estrogen-Only Menopause Therapy Linked to Reduced Alzheimer’s Brain Pathology

Women who used estrogen-only menopause hormone therapy showed fewer Alzheimer’s disease-related brain changes at autopsy and a lower risk of clinical dementia diagnoses compared to nonusers, according to a study published in the medical journal Neurology. Researchers analyzed records from more than 21,000 women across two large Alzheimer’s databases to examine the association between systemic estrogen-only treatments and late-life brain health.

Autopsy Findings and Biological Measures of Alzheimer’s

Brain autopsy results available for approximately 2,700 women in the study—including about 250 users of estrogen-only hormone therapy—revealed distinct differences in neurobiological hallmarks. After adjusting for confounding variables such as age, education, genetic predisposition, race, and high blood pressure, lead study author Jennifer L. Bruno, PhD, an instructor of psychiatry and behavioral sciences at Stanford Medicine in California, and her colleagues found that hormone therapy users had 35 percent lower odds of advanced Alzheimer’s-related brain changes. According to the research data, about 18 percent of hormone therapy users displayed no signs of Alzheimer’s disease pathology at autopsy, compared with roughly 10 percent of nonusers. Furthermore, about 40 percent of the hormone users exhibited high levels of Alzheimer’s-related brain changes, versus 51 percent of nonusers.

Jill M. Daniel, PhD, the Dohanich Professor in Brain Science and a professor of psychology at the Tulane University Brain Institute in New Orleans, who was not involved in the research, noted that the association between hormone therapy and biological measures is particularly interesting. Biological measures represent physical signs of the disease in the brain rather than external symptoms like memory loss, according to reporting by Everyday Health. In addition to autopsy findings, the study evaluated smaller groups of patients using blood or spinal fluid biomarker tests, brain imaging, and memory testing. The data showed that hormone users experienced 39 percent lower odds of a clinical dementia diagnosis along with lower odds of measurable memory problems than nonusers, according to Everyday Health.

Scope and Limitations of Estrogen-Only Therapy

Study co-author Jacob Shaw, a psychiatry resident at Massachusetts General Hospital/McLean Hospital noted that researchers accounted for confounding factors including age, race, and a history of hypertension, as reported by Scientific American. However, study authors emphasized that the findings demonstrate an association rather than a direct cause-and-effect relationship. Hadi Hosseini, a neuroscientist at Stanford University and the study’s senior author, pointed out that women who took estrogen-only hormone therapy might have been healthier overall or possessed better access to healthcare compared to those who did not, as reported by Scientific American.

Investigators also noted limitations regarding patient medical histories. The research datasets lacked specific records detailing why individual patients took estrogen-only therapy or whether they had undergone hysterectomies. Because estrogen-only regimens are linked to an increased risk of endometrial cancer, medical guidelines typically recommend them for women who have had a hysterectomy, while women with an intact uterus require a progestogen to protect the uterine lining, according to study authors cited by Everyday Health and Scientific American.

Timing Considerations and Future Clinical Research

The timing of when women initiate hormone therapy remains a critical missing piece in fully understanding these findings. Subjects in the research databases first reported taking estrogen in their 70s, an age group where hormone therapy is not generally recommended under modern clinical guidelines. Instead, current medical practice favors starting hormone therapy much closer to the onset of menopause, typically in a patient’s late forties or early fifties. Daniel indicated that it would be particularly useful to determine when the study participants initiated treatment, the duration of their use, and their complete hormone history prior to entering the databases, according to Everyday Health.

While previous research has raised the possibility of a critical window for estrogen treatment to positively impact the brain based on proximity to menopause, experts caution that it is still too early to recommend hormone therapy specifically for Alzheimer’s disease prevention. Bruno stated that the observational findings set the stage for future randomized controlled trials to clarify the complex relationship between menopause, estrogen, and long-term dementia risk, as reported by Scientific American.