BOSTON (AP) — 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.

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. What causes the mind-robbing disease isn’t known and there is no cure or any treatments that slow its progression.

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