Women who begin hormone replacement therapy in their late 40s or early 50s may face a significantly lower risk of developing dementia later in life, according to a new analysis of UK Biobank data. The study, published in the journal Alzheimer's & Dementia, found that women who started HRT between ages 46 and 56 had a 23% lower risk of all-cause dementia compared with those who never used the therapy.
Researchers examined health records from 183,450 postmenopausal women with an average age of 60, tracking them over a 13-year follow-up period. Overall, HRT use was associated with roughly a 10% lower risk of all-cause dementia and a 16% lower risk of Alzheimer's disease. The protective association was strongest among women who began therapy during the typical menopausal transition window and among those who had undergone surgical menopause. Starting HRT after age 56 showed no measurable reduction in dementia risk.
Dr. Alexa Fiffick, a board-certified family medicine physician and founder of Concierge Medicine of Westlake in Cleveland, Ohio, said the findings align with existing clinical observations. She stressed that the study is observational, meaning it cannot establish cause and effect. "So, it kind of stays where the data has been for a while — that in certain patients, we have no evidence that it really makes a difference," Fiffick told Fox News Digital. She noted that some groups, including women who experience menopause early, whether surgically or naturally, and those carrying the APOE ε4 genotype linked to higher dementia risk, may derive greater benefit.
The researchers themselves acknowledged the limitations of their work. Because the study was observational, it could not prove that HRT prevents dementia, only that an association exists. The analysis did not assess safety outcomes or adverse events related to HRT use. Women who choose hormone therapy may also differ from non-users in ways that influence dementia risk, including overall health, lifestyle habits, and access to healthcare. While the authors adjusted for many of these variables, they noted that unmeasured differences could still account for some of the observed effect.
The study also lacked detailed information about the specific types of hormone therapy used, the method of administration, or the dosages women took. Most participants were of European ancestry and tended to be financially better off, which means the findings may not apply equally to women from other backgrounds.
Fiffick cautioned that this single study does not justify seeking out HRT solely for dementia prevention. "However, if you're having symptoms, if you feel not yourself, come in, talk to your doctor, have that conversation," she advised. She pointed to existing data linking menopausal symptoms such as hot flashes and night sweats with vascular changes in the brain. "So, we are very hopeful to see that treating those symptoms may prevent the vascular changes that lead to vascular dementia, but we just don't have that data right now," she said.
Hormone therapy carries known risks that vary by formulation. Oral estrogen has been associated with an increased risk of blood clots, while transdermal options such as patches, gels, and creams do not appear to carry the same danger. Other types of HRT may affect breast tissue activity, inflammation levels, and cardiovascular markers. "So, it's not one size fits all, and it's really worth an extensive conversation," Fiffick said.
The U.K. research team plans to conduct randomized controlled trials to test whether HRT genuinely reduces dementia risk. Future studies will examine estrogen-only versus combined therapy, dosage amounts, administration routes, treatment duration, age at therapy initiation, menopause type, and potentially APOE genotype. Fiffick welcomed the direction of the research. "I think the more we have studies like this, the more we're going to propel forward the randomized controlled trials to really give women the data they deserve," she said. "Women deserve to have information to use to make decisions about their bodies."