Having a higher IQ or being active in your youth may dramatically lower the risk of developing dementia when you're older.

A new study shows that men and women who had higher than average intelligence or participated in a lot of extracurricular activities as high school students were up to half as likely to develop dementia by the time they reached their 70s.

Researchers say the results support the "reserve" theory of brain aging. According to this theory, people whose brains contain a greater network of interconnections from intelligence and extensive activity are able to withstand a higher degree of brain damage before developing dementia.

They say the study suggests that early intelligence may be a sign of the brain's reserve capacity, and involvement in activities may contribute to this reserve and reduce the risk of dementia in later life.

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Intelligence and Activity Reduce Dementia Risks

In the study, researchers looked at the relationship between intelligence and activity levels in youth and the risk of dementia in later life in a group of nearly 400 men and women who graduated from the same high school in the 1940s. The results appear in a recent issue of the Journal of the American Geriatrics Society.

All of the participants underwent IQ (intelligence quotient) testing at about age 15, and the IQ scores ranged from 79-149.

Researchers also measured the number of extracurricular activities the students were involved in each year using information from their high school yearbooks; that number ranged from zero to five.

The results showed that men and women who had a higher than average intelligence were about half as likely to have dementia by their mid-70s.

In addition, those who participated in two or more activities per year had a third lower risk of dementia compared with those who participated in fewer than two activities per year.

Researchers say that although the risk of developing dementia may be greater among those with lower intelligence, it also appears that adopting an active lifestyle can help reduce this risk.

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By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCE: Fritsch, T. Journal of the American Geriatrics Society, April 2005.