Two recent observational studies have renewed debate over whether menopause hormone therapy offers protection against Alzheimer’s disease, suggesting potential cognitive benefits but stopping short of providing definitive evidence.

One study, published in the journal Alzheimer’s & Dementia, analyzed health records from 183,450 postmenopausal women enrolled in the U.K. Biobank. About 4,000 of these women developed dementia over the study period. The findings indicated that women who underwent natural menopause and received hormone therapy had an 11 percent lower risk of Alzheimer’s disease compared to those who did not use the therapy. This risk reduction was more pronounced in women who experienced surgical menopause—generally through ovary removal—with a 32 percent lower risk of Alzheimer’s and a 26 percent lower risk of all dementias combined. The greatest benefits appeared among women who began hormone therapy between ages 51 and 56. However, the observed reduction in risk for all dementias among women with natural menopause was not statistically significant.

Anne-Marie Minihane, a professor of nutrigenetics at the University of East Anglia and lead author of this study, highlighted that hormone therapy’s effects could vary among different groups and emphasized the importance of treatment timing and individual risk factors such as family history of Alzheimer’s. The reasons for the larger benefits seen in women with surgical menopause remain unclear, but may relate to their generally higher baseline dementia risk.

A second study published earlier this month in Neurology presented neuropathological evidence suggesting that women who received estrogen-only hormone therapy exhibited fewer Alzheimer’s disease markers in their brains. This study included autopsy data showing reduced amyloid deposits, a hallmark of Alzheimer’s pathology, in women who had taken estrogen. The researchers, led by Jennifer Bruno of Stanford University, noted that the estrogen-only therapy was likely given to women who had undergone hysterectomies, though this could not be confirmed. Bruno stated that these findings provide additional support for a possible protective effect but cautioned that clinical decisions should not be based solely on this data.

Despite these promising signals, experts warn against overinterpreting the results because both studies rely on observational data, which cannot establish causation. Variables such as socioeconomic status and healthcare access, which influence both hormone therapy use and dementia risk, may confound the associations observed. Rebecca Thurston, associate dean at the University of Pittsburgh School of Medicine, described the findings as “thought-provoking” but emphasized the need for well-designed randomized clinical trials to clarify hormone therapy’s impact on Alzheimer’s risk.

Current evidence from clinical trials remains inconclusive. The Women’s Health Initiative, the largest trial to date, originally reported an increased dementia risk associated with hormone therapy, though its relevance to contemporary treatment practices has been questioned. Another trial, the Kronos Early Estrogen Prevention Study (KEEPS), involving younger women and modern hormone formulations, found neither cognitive benefit nor harm over follow-up periods.

Stephanie Faubion, clinical director at the Mayo Clinic Center for Women’s Health, pointed to unknowns regarding hormone formulations, dosage, and timing as factors limiting clinical recommendations. She stressed that the type of hormone therapy—such as estrogen alone versus combined estrogen-progesterone treatments—and administration method can significantly influence health outcomes, including brain effects.

As the debate continues, medical professionals urge women to consult healthcare providers for individualized guidance. The scientific community calls for further research, particularly randomized controlled trials, to determine if and how menopause hormone therapy might influence Alzheimer’s disease risk.