It would be deeply ironic, if hypothetical the dementia plaques were just "memory formation messengers" going awry and accumulating. So the source of decay would be usage and straining this finite machine build for decay results in even faster buildup. Now imagine the body starves, needs sugar donations from all donors, nothing special, happens every spring, and the brain used to donate these malformed memories, whisps of sugar. So dementia would corelate as a food oversupply disease with western lifestyle and social stability.