Consider your brain a muscle, and find opportunities to flex it. "Read, read, read," says Dr. Amir Soas of Case Western Reserve University Medical School in Cleveland. Do crossword puzzles. Play Scrabble. Start a new hobby or learn to speak a foreign language. "Anything that stimulates the brain to think." Also, watch less television, because "your brain goes into neutral," he said.

Challenging the brain early in life is crucial to building up more "cognitive reserve" to counter brain-damaging disease, according to Dr. David Bennett of Chicago's Rush University. And, reading-habits prior to age 18 are a key predictor of later cognitive function.

A cognitive psychologist in England found that when elderly people regularly played bingo, it helped minimize their memory loss and bolster their hand-eye coordination. Bingo seemed to help players of all ages remain mentally sharp

In a study of 193 people believed to have Alzheimer's disease, researchers found that people who participated in fewer leisure activities between the ages of 20 and 60 were 3.85 times more likely to develop Alzheimer's.

Most beneficial was spending time in intellectual pursuits. "A passive life is not best for the brain," said Dr. Robert P. Friedland at University Hospitals of Cleveland.

Physical exercise has a protective effect on the brain and its mental processes, and may even help prevent Alzheimer's disease. Based on exercise and health data from nearly 5,000 men and women over 65 years of age, those who exercised were less likely to lose their mental abilities or develop dementia, including Alzheimer's.

Furthermore, the five-year study at the Laval University in Sainte-Foy, Quebec suggests that the more a person exercises the greater the protective benefits for the brain, particularly in women.

Inactive individuals were twice as likely to develop Alzheimer's, compared to those with the highest levels of activity (exercised vigorously at least three times a week). But even light or moderate exercisers cut their risk significantly for Alzheimer's and mental decline.