WASHINGTON, D.C.: Studies suggest that keeping the brain and body spry in middle age staves off later cognitive decline, but scientists are unsure why. A paper suggests that contrary to some thinking, it may have nothing to do with changing the course of Alzheimer’s pathology. Researchers led by Prashanthi Vemuri, Mayo Clinic, Rochester, Minnesota, report that in the population as a whole, as people aged, their brains accumulated amyloid, shrank, and became less active regardless of their mental and physical prowess in midlife. Highly educated carriers of the ApoE4 allele were an exception. They better maintained neural activity in later life, and if they also kept up cognitive stimulation, they accumulated less amyloid. “Until now, no studies had examined if imaging biomarker trajectories correlated with physical and cognitive activities in midlife,” Vemuri said…