What we know about estrogen's effect on the brain.

Cognitive impairment and Alzheimer's disease are growing problems as our population ages. Although estrogen appears to beneficially effect neurons, evidence that hormone therapy improves cognition or prevents dementia is limited. All studies are hampered by difficulties in strict dementia ascertainment and confounding due to cognitive testing while observational studies are biased by the healthy hormone therapy user effect. Does estrogen preserve cognition? Some studies demonstrated a small improvement in generally healthy women, but some found no effect. Does estrogen prevent Alzheimer's disease? Many case-control and two cohort studies reported a sizeable benefit of hormone therapy, but many did not adequately adjust for confounders and there are no randomized controlled trial data yet. Does estrogen improve function in women with Alzheimer's disease? A large randomized controlled trial demonstrated no beneficial effect of conjugated estrogen on clinical outcomes in women who already had mild to moderate Alzheimer's disease.