Crossword puzzles and chess will keep your mind sharp—right? Maybe not. If you do a puzzle every day and you’re really good at it, it’s probably not the kind of task required to give your mind a workout. As we age, we need to challenge our brains with both new and hard stuff, write the authors of The Menopause Book. Learning to play a musical instrument, mastering a new language—or even finding a tougher chess opponent—might qualify.