I admit to doing an hour of all different kinds of puzzles - word, number, and spacial relations puzzles every day and always have a book that I’m reading.
My mom developed ALZ in her 60s and died at 78. My grandmother lived to be 94 and only had some age related dementia at the very end. My grandmother did puzzles and read novels every single day. Anecdote of one, but I’m willing to do the puzzles just in case.