Midlife Brain Remodeling Rewrites Immune Landscape, Linking to Inflammation and Dementia Risk

A Science study of ~320,000 hippocampal cells from 40 healthy people aged 20–95 finds a midlife tipping point around age 50, where aging brains undergo extensive cellular remodeling: original microglia appear replaced by blood-derived monocytes, astrocytes lose energy-related activity and decline, and 3D genome organization degrades, leading to higher inflammation and a potential dementia risk, with some differences between men and women.