27/08/2026
We are seeing an increasing amount of research focussed on oestrogens and cognition. Every study adds to our understanding of the topic.
Here is a large observational UK Biobank study from Squires et al. exploring the association between Hormone replacement therapy and dementia risk among postmenopausal women.
In this study, in 183,450 postmenopausal women from the UK Biobank (mean 13.3 years follow-up), multivariable Cox regression models evaluated associations between HRT use (≥1 year) and all-cause dementia and dementia subtypes. Stratified analyses assessed modification by menopause type, lifetime estrogen exposure, apolipoprotein E (APOE) ɛ4 genotype, and age at HRT initiation.
Over 2.43 million person-years, 3,948 dementia cases were identified. HRT use was associated with lower all-cause dementia (hazard ratio [HR] 0.90; 95% CI, 0.84-0.96), with stronger associations in surgical menopause (0.74, 0.65-0.84), APOE ɛ4 carriers (0.87, 0.80-0.95) and women with lower endogenous estrogen exposure (0.84, 0.77-0.93). Initiation between ages 46 and 56 conferred the greatest benefit.
The authors concluded that HRT use was associated with lower dementia risk, and these findings may help inform more tailored approaches to HRT prescribing in relation to women's lifetime dementia risk.
Strengths of the study - large amount of available data, follow-up for dementia diagnosis and long follow-up. Women were stratified into various subgroups to show that the association between HRT and dementia risk varies considerably.
Limitations of the study - results are associations and not causal. HRT use is subject to selection (healthy-user) bias, as women who use HRT can differ systematically from non-users including socioeconomic status, educational attainment, ethnicity, and lifestyle factors. Also, lack of information on HRT formulation, dose, and route of administration and potentially participants disproportionally drawn from more socioeconomically advantaged groups.
Observational studies don’t necessarily prove or disprove theories facts, or conclusions. But every little evidence adds to our understanding of long-term effects of HRT and are valuable in counselling patients on benefits and risks.
https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.71679