"I enjoy playing scrabble from time to time. It keeps me thinking about words and it's fun."

"I do the Sunday crossword puzzle every week to keep my mind active."

It's an idea that's really caught on: that exercising your brain regularly with puzzles, for example. Can keep your mind sharp and ward off dementia and Alzheimer's disease.

And it's become big business.

Today you can find video games‚ DVDs and special software that promise to keep you mentally fit. There are also subscription web sites, which charge about $100 a year for an array of brain-boosting games.

In a way, it makes sense: just as physical activity can keep your body strong,

Mental exercise can keep your brain in shape. But is it really true?

Studies show that brain training can help improve your memory, but that's different from warding off dementia.

And people who do stimulating activities like reading,

Learning a new language,

Or playing a musical instrument have lower rates of dementia and Alzheimer's. But this doesn't necessarily prove cause and effect.

So the bottom line: The jury is still out. Still, it's a good idea to keep your mind active, but you don't need to spend a lot on special products.

Anything from crossword puzzles to challenging board games can do the trick.

Perhaps the best thing for your brain is regular physical activity. Research shows it can help improve older people's ability to remember and process information more quickly.

So next time you forget where you parked your car, don't sweat it. Just seize the opportunity to go for a walk. Your brain will thank you!