BRAIN EXERCISE: New research boosts the "use it or lose it" theory about brainpower and staying mentally sharp. People who delay retirement have less risk of developing Alzheimer's disease or other types of dementia, a study of nearly half a million people in France found.
THE REASONS: Researchers say the conclusion makes sense. Working tends to keep people physically active, socially connected and mentally challenged — all things known to help prevent mental decline.
ABOUT DEMENTIA: About 35 million people worldwide have dementia, and Alzheimer's is the most common type. In the U.S., about 5 million have Alzheimer's — 1 in 9 people aged 65 and over.