May 7, 2008 -- Mentally demanding jobs come with a hidden benefit: less mental decline with age.
Work that requires decision making, negotiating with others, analysis, and making judgments may not necessarily pad your bank account. But it does build up your "cognitive reserve" -- a level of mental function that helps you avoid or compensate for age-related mental decline.
"Jobs that have elements where you need to solve problems, plan and organize, and think flexibly and on your feet appear to carry cognitive benefits throughout your life. You can potentially draw on them later as reserves," Duke University psychologist Guy G. Potter, PhD, tells WebMD.
Potter and colleagues studied 1,036 World War II veterans who agreed to take mental-status tests every three or four years beginning in 1990. More than half of the 70-ish men were twin pairs included in the ongoing Duke Twin Study of Memory in Aging.
Earlier work with the twins suggested that the twin who had the more complex job had a lower risk of age-related dementia. That led to the current study, funded by the National Institute on Aging and the Alzheimer's Association.
In their expanded study, Potter and colleagues took advantage of the fact that the men had taken an IQ test when they entered the Armed Services. This allowed them to compare the mental function of men with equal intelligence, but who'd worked at jobs that demanded different levels of complexity.
"You may say those who did not get dementia were smarter to start with, or that those with higher complexity jobs got them because they were smarter to start with," Potter says. "We wanted to know whether it was the intelligence they were born with that gave them a golden ticket to aging, or something else."
After taking into account both intelligence and education, Potter and colleagues found that men with more complex jobs -- in terms of general intellectual demands and human interaction and communication -- performed significantly better on tests of mental function.
Strikingly, this effect was stronger for men who, earlier in life, scored in the low/average range on intelligence tests. For men with high IQ scores early in life, job complexity had only a small effect on later mental function.
"People who may have had less of an intellectual gift, or who may have been socially disadvantaged, got something more out of having complex jobs," Potter says. "So maybe you can ride an intellectual gift further if you have it early in life, whereas those who don't have those gifts may gain them later in life."
Men whose jobs required mostly physical activity scored somewhat lower on mental function tests, but Potter discounts the significance of this finding.
"What I don't want is for people to look at the manual-labor finding and worry that if they have a noncomplex job, it is not beneficial. The physical aspect of work has some benefits as well," he says. "The balance you need is between physical and mental effort in work and in leisure. Some manual jobs have benefits in their own right."
And, Potter warns, not all complex jobs are healthful.
"Complex jobs are stressful jobs," he says. "That is something we'll be working on, trying to parse out the complex jobs that give a sense of accomplishment and the complex jobs that give you a lot of stress. Not all complex jobs are beneficial, and we hope to work that out somewhere down the line."
Potter and colleagues report their findings in the May issue of the journal Neurology.