What I've read is that e.g. doing Sudoku puzzles won't save you from dementia, but you'll be starting from a higher point so that you'll be older when you reach

What I've read is that e.g. doing Sudoku puzzles won't save you from dementia, but you'll be starting from a higher point so that you'll be older when you reach a certain diminished level than if you didn't exercise your abilities beforehand--use it or lose it (sooner).