(AP) — New research boosts the “use it or lose it” theory about brainpower and staying mentally sharp.

A study of nearly half a million people in France finds that people who delay retirement have less risk of developing Alzheimer’s disease or other types of dementia.

Researchers found that for each additional year a person worked, the risk of getting dementia was reduced by more than 3 percent.

Doctors say the conclusion makes sense. Working helps keep people physically active, socially connected and mentally challenged, and all of those things help prevent mental decline.

The French government’s health research agency did the study. Results were reported Monday at the Alzheimer’s Association International Conference in Boston.