British researchers have concluded that to keep your brain sharp as you age you need to keep it busy.

It turns out that the more regularly adults ages 50 and up played puzzles such as crosswords and Sudoku, the better their brain functions.
You don't need to solve quadratic equations, just come up with a four letter word for domicile!
The people who played games and solved puzzles wee found to  perform better on tests assessing attention, reasoning, and memory compared to those who did puzzles less often or not at all. Researchers calculate that people who engage in word puzzles have brain function equivalent to ten years younger than their age on tests assessing grammatical reasoning, and eight years younger than their age on tests measuring short term memory.
Researchers say the can't conclude that playing these puzzles necessarily reduces the risk of dementia in later life but the research supports previous findings that indicate regular use of word and number puzzles helps keep our brains working better for longer.