Researchers analysed data from 180,000 postmenopausal women in the UK, the largest study of its kind, and found a consistent link between HRT use and reduced dementia diagnoses. The association was strongest for Alzheimer's disease, the most common form of dementia, with a 16% lower risk among HRT users compared to non-users. The study adjusted for known risk factors such as age, socioeconomic status, and medical history, but as an observational study it cannot rule out that women who choose HRT may be healthier in other ways.

The findings come amid shifting attitudes toward menopause treatments. Hormone replacement therapy, once widely prescribed for menopausal symptoms, saw a dramatic decline in the early 2000s after the Women's Health Initiative study linked it to increased risks of breast cancer, heart disease, and stroke. Subsequent reanalyses and follow-up studies have suggested the risks are lower for younger women and those using modern formulations, leading to a gradual rehabilitation of HRT in clinical guidelines.

Dementia remains a major global health challenge, with around 55 million people living with the condition worldwide and women disproportionately affected. The biological plausibility of a protective effect of estrogen has long been debated. Estrogen receptors are abundant in brain regions involved in memory and cognition, and animal studies have suggested estrogen may support neuronal health and reduce inflammation. However, previous human studies have produced conflicting results, with some showing no benefit or even increased risk.

The lead author of the new study, speaking on condition of anonymity pending formal publication, described the findings as 'reassuring' but emphasised that women should not start HRT solely to prevent dementia. 'These results suggest HRT does not increase dementia risk and may offer some protection, but the absolute risk reduction is modest,' they said. 'The decision to use HRT should remain a personal one, made with a healthcare provider, balancing symptom relief against individual risks.'

Independent experts urged caution. Dr. Eleanor Finch, an epidemiologist at the University of Manchester not involved in the study, noted that observational studies can be confounded by factors such as health-conscious behaviour among HRT users. 'Women who seek out HRT may also be more likely to exercise, maintain a healthy diet, and have better access to healthcare — all of which independently reduce dementia risk,' she said. 'While this is a high-quality study, it does not establish cause and effect.'

The research is expected to inform ongoing discussions about menopause care and dementia prevention. Current guidelines in the UK and US recommend HRT primarily for managing menopausal symptoms, not for preventing chronic diseases. The new data may encourage further investigation into whether specific formulations, timing, or duration of treatment influence cognitive outcomes.