Can puzzles reduce the risk of dementia?

An article in The Herald (UK) suggests that its puzzle page might have therapeutic benefits:

...puzzles such as The Herald's giant crossword published today, chess, the number game Sudoku and IQ tests are today seen as the tools to give users a rigorous mental workout. They can improve mental age by up to 14 years, so the scientists claim.

Scientists have found the neurological equivalent of an untoned body could lead to a drastic dulling of cerebral powers. Most worryingly, an under-stretched mind may put some individuals at increased risk of dementia in later life.

Next time someone asks why you spend so much time on chess, tell them it's a better choice than medication.