For decades, the relationship between estrogen and the aging brain has occupied a quiet corner of medical inquiry, and a new study of more than 21,000 women has added a meaningful chapter to that story. Researchers found that women who used estrogen-only hormone therapy in later life carried notably lower odds of developing dementia and showing Alzheimer's disease markers in the brain — a finding that invites cautious hope without yet offering clear answers. The science reminds us that the body's chemistry is deeply entangled with time, and that what we do, and when we do it, may shape the min