For decades, the question of whether estrogen might shield the aging brain from dementia has lingered at the edge of medicine's understanding. A new study of more than 21,000 women, published in Neurology, adds a meaningful chapter to that inquiry: women who used estrogen-only hormone therapy after age 70 showed markedly fewer biological signs of Alzheimer's disease and were nearly 40 percent less likely to receive a dementia diagnosis. The researchers are careful to frame this as association rather than causation, and the gap between historical prescribing practices and today's protocols mean