A surprising new study suggests that an anti-aging drug could help protect people genetically predisposed to Alzheimer's disease. Researchers found that just four weeks of low-dose rapamycin improved brain blood flow in healthy middle-aged adults carrying the high-risk APOE4 gene variant, with women showing the strongest benefits. Because declining blood flow can occur years before Alzheimer's symptoms appear, the discovery raises hopes for preventing or delaying the disease before memory loss begins.