Most of us think of Alzheimer’s as something that “just happens” in our 70s or 80s. In reality, the changes that lead to Alzheimer’s usually begin quietly in midlife—often 20 to 30 years before the first noticeable memory problems. Understanding this earlier timeline is empowering because it means the choices you make in your 40s, 50s, and 60s can meaningfully influence your brain health later on.