APOE4 May Shrink Brain Cells Years Before Alzheimer's…

APOE4 May Shrink Brain Cells Years Before Alzheimer's Symptoms Appear, and Scientists Found a Way to Reverse It in Mice APOE4, carried by roughly one in four people, is the strongest known genetic risk factor for Alzheimer's disease. A new study published in Nature Aging offers a genuinely important piece of the puzzle, mapping out exactly how this gene begins altering brain cells years before any memory problems become noticeable, and identifying a specific molecular target that reversed these changes in mice. Why this question matters: APOE4 is estimated to occur in 60 to 75% of people with Alzheimer's disease, making it a genuinely significant risk factor. Earlier research had already found signs of unusually high brain activity in human APOE4 carriers well before middle age, and this early hyperactivity has also been linked to later cognitive decline. However, exactly how APOE4 produces these early cellular changes, and why they might contribute to memory problems decades later, has remained unclear until now. The study: Researchers studied brain activity recordings and individual neurons from young mice carrying APOE4, focusing specifically on the hippocampus, a brain region central to memory. They compared these mice to others carrying APOE3, a version of the gene associated with lower Alzheimer's risk in humans. The key finding, early hyperactivity predicts later decline: Y