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DURHAM, NC – Doing a job that is intellectually demanding creates thinking abilities that pay dividends into retirement -- regardless of intelligence or years of education, according to new research from the Duke University Medical Center.

"Our society is expected to live and work longer than previous generations, so we sought to understand how an individual's occupation affected cognition later in life," said Guy Potter, PhD, assistant professor of psychiatry at Duke and the study's lead author. "Our study found that jobs with more intellectual demands were associated with better performance in memory and other cognitive abilities post-retirement, even after accounting for the influences of age, education and intelligence."

The study, published in the May issue of the journal Neurology, looked at 1,036 male twins who participated in the Duke Twins Study, which included World War II veterans who were given a test to determine their general learning abilities when they joined the military in the early 1940's.

The participants completed follow-up assessments to evaluate their cognitive status every three to four years beginning when they were in their 60's. This is believed to be the first study to evaluate intelligence early in life in conjunction with the influence of job characteristics and cognition in later life.

The researchers found that the cognitive benefits associated with intellectually demanding jobs were greatest among people who had lower scores on intelligence tests in their youth. In contrast, physically demanding work was associated with a decrease in cognitive performance later in life.

"Although the intellectual and physical demands of an individual's job are not the largest factors influencing cognitive performance as we age, this study illustrates how a number of smaller influences like these can accumulate over the lifespan to have a positive or negative effect on brain health in later life," Potter said. "Unlike age or intellect, job demands are something that an individual can potentially modify to optimize their cognitive reserve."

"Most of us spend a significant portion of our adult life at work and we may actually be benefiting from the intellectual demands placed upon us," Potter added.

Researchers also offered caution about the finding that manual labor is associated with worse cognitive performance in later life. "Physical exertion has health benefits in its own right. It is important for people to find a place for both mental and physical activity in their lives, and for researchers to offer insights about how this can best be achieved," Potter explained.

This study was supported by grants from the NIH and Alzheimer's Association. Other contributing authors include Michael J. Helms, BS, and Brenda Plassman, PhD.