Hormone therapy not linked to dementia risk, review finds

Menopause hormone therapy is not strongly linked to dementia, a review of health data from over one million women reports.

The systematic review, commissioned by the World Health Organization, examined links between cognitive health and hormone replacement therapy (HRT).

The WHO currently provides no specific guidance on dementia and HRT, despite recent controversy around the topic.

Researchers at University College London conducted the analysis, which found inconsistent and slight associations with dementia across studies, some positive and some negative, but all with very low certainty.

Lead author Melissa Melville, an ageing cognition researcher, said: “Menopause hormone therapy is widely used to manage menopausal symptoms, yet its impact on memory, cognition, and dementia risk remains one of the most debated issues in women’s health.

“Conflicting research and concerns about potential harms have fuelled public and clinical debate, leaving women and clinicians unsure whether menopause hormone therapy might raise or reduce their risk of dementia.”

HRT replaces ovarian hormones after menopause and is used to treat symptoms such as hot flushes, night sweats, poor sleep, low libido and osteoporosis.

Most studies included in the review were observational, meaning they cannot prove cause and effect.

Formulations, doses and prescription timing varied considerably, making comparisons difficult.

Only one randomised controlled trial (participants are randomly assigned to treatments) found that oestrogen-only products may increase dementia risk in women over 65, but the researchers said certainty was low.

The absolute risk difference was 6.27 additional cases per 1,000 women.

Senior author Aimee Spector, a clinical psychologist at UCL, said: “This review will help to inform the upcoming WHO guidelines on reducing the risk of cognitive decline and dementia, which are expected to be released in 2026.

The findings support a 2024 Lancet Commission on dementia, which also found insufficient evidence to suggest HRT increases or decreases dementia risk.

They also align with the US Food and Drug Administration’s announcement detailing plans to remove warnings on HRT products that had cautioned about increased dementia risk.

The researchers concluded: “Overall, available evidence to date does not support MHT solely for risk reduction of dementia nor does MHT increase dementia risk.”

“There is a need for further high-quality research to clarify the role of MHT in relation to dementia.”

The team called for further data on those who enter menopause prematurely, either through hysterectomy, where the uterus is surgically removed, or oophorectomy, where one or both ovaries are removed.