The best way to prevent dementia is to keep the mind active, whether it's by reading books, doing crossword puzzles, playing sudoku, or participating in other creative endeavors, says Kennedy.

CNN: Study: Ginkgo doesn't cut dementia risk

Ruma knew that the house, with the rooms her mother had decorated and the bed in which she liked to sit up doing crossword puzzles and the stove on which she'd cooked, was too big for her father now.

NPR: Excerpt: 'Unaccustomed Earth'

Reading, going to work and navigating a busy life may be enough to maintain brain health, but lifting performance takes massive amounts of practice--learning a new language, taking regular music lessons, doing complex jigsaw puzzles--to produce enough chemicals to make synapses stronger.

FORBES: Innovation

During her years at Marian, where she majored in theology, it became clear to her that she was doing more than just exercising her brain, as she might with crossword puzzles.

FORBES: 85-Year-Old Graduates From College -- And Finds A Job