Study: Hormone Therapy Linked to Lower Risk of Dementia and Alzheimer’s in Women

A large UK study has shown that postmenopausal women who used hormone replacement therapy were less likely to develop dementia and Alzheimer’s disease, with stronger associations observed in certain groups, including women who underwent surgical menopause or had a genetic predisposition to Alzheimer’s.

Researchers from the Universities of East Anglia and Exeter in the UK said the findings could help identify women most likely to benefit from hormone therapy in the future, but emphasized that the study is observational and does not prove that the treatment itself prevents dementia.

The study, published in the journal Alzheimer’s & Dementia, analyzed data from 183,450 postmenopausal women registered in the UK Biobank. Researchers followed their health for an average of 13.3 years, during which approximately 4,000 cases of dementia were recorded.

Hormone Therapy for Women and Alzheimer’s

Results showed that women who used hormone replacement therapy for at least one year were about 10% less likely to develop dementia compared to those who never used it, while the risk of Alzheimer’s disease—the most common form of dementia—was reduced by 16%.

Dr. Anne-Marie Mynahane, a researcher involved in the study from the Norwich Medical School at the University of East Anglia, said the treatment’s effect was not uniform across all women, and biological and genetic differences appeared to be important factors in the strength of the association.

The greatest reduction was seen among women who experienced surgical menopause, such as those whose ovaries were removed, where hormone therapy use was linked to a 26% lower risk of any type of dementia compared to non-users.

Hormone therapy also appeared more beneficial for women who naturally produced lower levels of estrogen during their lives, due to late onset of menstruation or early menopause, with dementia risk reduced by about 16% in this group.

Researchers also found that the protective association was stronger among carriers of the APOE4 gene variant, one of the most significant known genetic risk factors for Alzheimer’s disease.

Scientists believe hormonal changes accompanying menopause may be one factor explaining the higher incidence of Alzheimer’s in women, alongside longer life expectancy and the impact of certain genetic risk factors.

The study also suggested that timing of therapy initiation might matter; women who started treatment between ages 46 and 56 recorded the greatest reduction in dementia risk.

Researchers noted that this finding supports the so-called “critical window hypothesis,” which proposes that hormone therapy may be more beneficial for the brain if started near the transition to menopause, rather than later in life.

Hormone Therapy and Brain Health

Hormone replacement therapy is primarily used to compensate for declining sex hormones and relieve menopausal symptoms such as hot flashes and night sweats, but its potential impact on brain health has remained a subject of scientific debate.

Dr. David Llewellyn, a co-researcher from the University of Exeter Medical School, said the significance of the results lies in shifting the focus from whether hormone therapy affects dementia overall, to identifying “which women might benefit and when.”

However, researchers cautioned against interpreting the findings as proof that hormone therapy is a proven preventive measure against dementia, as other health, social, and behavioral factors could influence the relationship observed in the study.

The research team said the results pave the way for further studies exploring the possibility of developing more personalized approaches to hormone therapy use, taking into account the type of menopause, genetic factors, duration of lifetime estrogen exposure, and age at therapy initiation.