A simple brain-training program that sharpens how quickly older adults process visual information may have a surprisingly powerful long-term payoff. In a major 20-year study of adults 65 and older, those who completed five to six weeks of adaptive “speed of processing” training — along with a few booster sessions — were significantly less likely to develop dementia, including Alzheimer’s disease, even two decades later. Participants who received the boosted speed training had a 25% lower dementia risk compared to those who received no training, making it the only intervention in the trial to show such a lasting protective effect.