This study was not a clinical trial so cannot prove cause and effect. The WHI showed that estrogen, with or without progestin, increased the risk of Alzheimer’s and atrophied the hippocampus and frontal lobe. KEEPS also showed HRT in newly menopausal women caused greater brain atrophy, ventricular expansion, and white matter hyperintensities. So while these women were too young to show increased dementia risk, they did experience impaired verbal learning (Premarin) or impaired event recall and greater subjective memory complaints (estradiol). Moreover, a study last year of APOE carriers found they have greater levels of ER alpha in their hippocampi, which theoretically would make exogenous estrogen particularly risky.
Bottom line – HRT does not prevent dementia. On the contrary, there is actually a new clinical trial out of Stonybrook testing the aromatase inhibitor letrozole (an antiestrogen used to treat and prevent breast cancer) to see if it will slow Alzheimer’s progression. I suspect THIS will actually work.