I have a friend in early 70s with Alzheimiers in her family and she does games and puzzles etc specifcally created for the purpose keeping the brain muscles active to slow down deterioration.
I do other stuff as I can’t handle games. One is memorizing verses.
One of the things I do to stay active and alert is walk around the neighborhood in my jammies and oven mitts down the middle of the road and count the horn honks. Math is good for the mind.