The most comprehensive study yet undertaken, incorporating the most reliable risk estimates so far achieved, has shown that hormone replacement therapy (HRT), also known as menopausal hormone therapy (MHT), did not increase the risk of dementia in women. The research team was led by Dr Yana Vinogradova of the School of Medicine of the University of Nottingham in the UK, but included experts from two other British universities, namely Oxford and Southampton.

The researchers used data from two of Britain’s largest medical databases, the Oxford University-based QResearch and the UK Department of Health’s Clinical Practice Research Datalink. The study used data for 615 917 women, aged 55 and older, gathered from 1998 to 2020. Of these, 118 501 had been diagnosed with dementia while the other 497 416, who had not been diagnosed with dementia, acted as the control group for the study.

Previous research, using much smaller data samples, had suggested a link between HRT/MHT and the development of Alzheimer’s disease. The Women’s Health Initiative Memory Study in the US had had a total sample size of just 7 479 women (aged 65 and above), and had suggested a link between combined oestrogen-progestogen treatment and increased risk of dementia. A Finnish study published in early 2019, which used a sample of almost 85 000 Finnish post-menopausal women, had suggested a very small link between pure oestrogen HRT/MHT and the risk of developing dementia.

The newly published and massively bigger UK study brings, in the words of the research team, “clarity to previously inconsistent findings and should reassure women in need of menopausal hormonal therapy. ... [T]his study provides the most detailed estimates of risk for individual treatments, and results are in line with existing concerns in guidelines about long term exposures to combined hormone therapy treatments.”

No overall associations between HRT/MHT use and the risk of developing dementia were found by the UK study. Differences in treatments and application methods (such as creams, devices, patches or pills) had no effect on dementia risk. Neither did treatment dosages nor durations.

“We are happy to be able to report findings that will reassure women needing menopausal hormone therapy and facilitate conversations between doctors and patients about the safest treatments,” affirmed Vinogradova. “We hope they will also be useful to other health professionals and policy makers.” The research was funded by the National Institute for Health Research School for Primary Care Research, a UK state agency.