Doing crosswords etc. can keep your mind sharper to a later age. My mother loved doing jigsaw puzzles, word searches, and crosswords until around age 90. Even for a year or so after dementia started being noticed, I would read her the clues and she would answer with some prompting. When we sold the house, we had to give away 95 jigsaw puzzles! She had us put them up in the attic when finished with hem (counted them!).