Published on: Dec 22, 2025
A comprehensive review of existing research has found no evidence that menopausal hormone therapy (MHT), also known as hormone replacement therapy (HRT), either increases or reduces the risk of dementia in postmenopausal women. The study, led by researchers at University College London with support from the University of Exeter, was commissioned by the World Health Organisation and published in The Lancet Healthy Longevity.
The findings help clarify a long-standing and controversial issue in women’s health and support current clinical guidance that decisions about MHT should be based on its known benefits and risks for menopausal symptoms, not on dementia prevention.
The review, the largest and most rigorous of its kind to date, analysed data from more than one million women across one randomised controlled trial and nine observational studies. Researchers found no meaningful association between MHT and dementia, mild cognitive impairment, or Alzheimer’s disease. Further analyses examining the timing, duration, and type of hormone therapy also showed no effect, including in women who experienced early menopause.
Professor Chris Fox from the University of Exeter Medical School noted that concerns about dementia are common among women considering MHT, but emphasized that current evidence shows it neither raises nor lowers dementia risk, and should not factor into treatment decisions for that purpose.
The study follows a recent U.S. FDA decision to remove previous “black box” warnings on hormone therapy that had cited unproven long-term risks, including dementia. While the FDA also suggested a possible protective effect against Alzheimer’s disease, this new review found no evidence to support that claim.
Lead author Melissa Melville highlighted that dementia disproportionately affects women worldwide, making it critical to identify genuine risk factors and prevention strategies. However, despite widespread use of MHT and ongoing debate, the review concludes that hormone therapy does not influence dementia risk.
Researchers caution that the evidence base is limited by a lack of high-quality, long-term randomised trials, particularly among women from ethnic minority backgrounds and those with early menopause or existing cognitive impairment. They stress the need for further robust research to better understand long-term cognitive outcomes.
Senior author Professor Aimee Spector added that the findings will help inform forthcoming WHO guidelines on reducing cognitive decline and dementia risk, expected in 2026, while underscoring that more long-term data are still needed.
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