A high IQ in adolescence and greater participation in various extracurricular activities may decrease a person's chances of developing dementia later in life, according to a study in the current Journal of the American Geriatrics Society.

The study found that persons who were more active in high school and who had higher IQ scores were less likely to have mild memory and thinking problems when they got older. Conversely, those who were lower on the IQ continuum and who participated in fewer activities in high school had a higher risk of cognitive decline.

Dementia refers broadly to neurological conditions that cause decline in memory and thinking abilities (cognition) and the ability to perform activities of daily living.

Alzheimer's disease is the most common cause of dementia in persons 65 years of age or older. It's been estimated that 4.5 million people in the U.S. have the Alzheimer's disease.

The new findings "add to a growing body of knowledge that dementias, such as Alzheimer's disease, may have a very long-term course, perhaps starting decades before clinical symptoms emerge," said study author Dr. Thomas Fritsch, of Case Western Reserve University in Cleveland, Ohio.

"They also indicate that the risk for dementia late in life may be decreased by maintaining an active lifestyle as a teenager," he added. "However, this conclusion is based on only one study and must be confirmed in other research."

He and colleagues studied 396 volunteers (mean age 75 years) who had all graduated from the same high school in the mid-1940s. With the participants' permission, student records were used to obtain adolescent IQ scores and activity levels were determined from yearbooks.

Adult cognitive status was determined through telephone screening. In cases in which cognitive impairment was indicated, a proxy respondent was interviewed.

The researchers observed a significant independent link between high adolescent IQ and a lower risk for dementia/mild cognitive impairment, even after adjusting for sex and education level.

Greater activity levels in youth were also independently associated with a reduced risk of dementia/mild cognitive impairment.

Fritsch emphasized, however, that while this research implicates a role for IQ and activity level in youth with later dementia risk, "many other factors, alone or in combination, also influence who will and will not develop dementia."

SOURCE: Journal of the American Geriatrics Society July 2005.