BOSTON — 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.
It’s by far the largest study to look at this, and 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.
“For each additional year of work, the risk of getting dementia is reduced by 3.2 percent,” said Carole Dufouil, a scientist at INSERM, the French government’s health research agency.
She led the study and gave results Monday at the Alzheimer’s Association International Conference in Boston.
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.
France has had some of the best Alzheimer’s research in the world, partly because its former president, Nicolas Sarkozy, made it a priority. The country also has detailed health records on self-employed people who pay into a Medicare-like health system.
Researchers used these records on more than 429,000 workers, most of whom were shopkeepers or craftsmen such as bakers and woodworkers. They were 74 on average and had been retired for an average of 12 years.
Nearly 3 percent had developed dementia but the risk of this was lower for each year of age at retirement. Someone who retired at 65 had about a 15 percent lower risk of developing dementia compared with someone retiring at 60, after other factors that affect those odds were taken into account, Dufouil said.
To rule out the possibility that mental decline may have led people to retire earlier, researchers did analyses that eliminated people who developed dementia within five years of retirement, and within 10 years of it.
“The trend is exactly the same,” suggesting that work was having an effect on cognition, not the other way around, Dufouil said.
France mandates retirement in various jobs — civil servants must retire by 65. The new study suggests “people should work as long as they want” because it may have health benefits, she said.
Tips to boost brain health
You may be able to help keep your brain in shape, not just the rest of your body. A large study in France suggests that delaying retirement and working until later in life may help prevent dementia.
Some other things the Alzheimer’s Association suggests for healthy aging:
• Stay active. Many studies show exercise reduces dementia risk.
• Stay connected — join a club, travel, volunteer. Social ties boost brain health.
• Eat right. High cholesterol may contribute to stroke and brain cell damage, while dark vegetables and fruits may help protect brain cells.
• Do mentally challenging activities such as word puzzles and other things that stimulate thinking skills.