There is growing scientific support for a neuroprotective role of estrogen in women as they age, even as the question still exists as to whether there are risks to brain function that could outweigh the benefits of postmenopausal hormal replacement.
In a new study (Differences in regional brain metabolism associated with specific formulations of hormone therapy in postmenopausal women at risk for AD, Psychoneuroendocrinology (2011) 36, 502-513), Daniel H.S. Silverman et al. publish the results of a prospective, randomized longitudinal clinical trial in which postmenopausal women age 50-65 on different formulations of hormone replacement therapy and at increased risk for Alzheimer's disease were evaluated with cognitive tests and functional brain imaging with positron emmission tomography (PET) at baseline and after two years of either treatment with, or discontinuation of, hormone replacement therapy.
They were able to show evidence of relative preservation of function in specific brain regions in all the women that was associated with longer esposure to bodily estrogen (age of menopause minus age of menarche). Moreover, women taking bio-identical 17-beta estradiol (E) performed far superior to women on congugated equine estrogens (CEE) on tests of verbal memory, and had higher functional measures in language and verbal memory areas of their brains on the PET scans. Women taking progesterone-plus-estrogen compounds had lower function scores compared to women on unopposed estrogen in other specific brain regions.
These findings further support a neuroprotective role for estrogen, at least in middle age women at increased risk for the future development of AD. How these results can be generalized to all women remains to be seen, however, this study supports the idea that current decisions about whether a woman should take hormone replacment therapy after menopause, how long she should take it for, and in what formulation she should take it, should consider her risk profile for future AD and should consider 17-beta estradiol as the estrogen to use. Whether natural micronized progesterone mitigates these benefits less than synthetic medroxy-progesterone acetate remains to be determined by future studies.