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MILWAUKEE - People who developed Alzheimer's disease tended to hold jobs with lower mental demands during their 30s, 40s, and 50s than people who did not get the disease, according to new research.
The study is the latest in a growing body of research suggesting that higher levels of education as well as mentally stimulating activities may offer some protection against a disorder that now affects 4.5 million Americans, a number that is expected to grow dramatically in the coming decades.
The study is the first look at mental job demands over the course of several decades and link those demands to Alzheimer's. An extensive U.S. Department of Labor ranking of occupational demands was used to determine mental and physical job demands.
Examples of jobs with high mental demands included engineers, doctors, science and math teachers, architects, computer programmers and journalists. Jobs with lower levels included janitors, construction laborers, machine operators, assemblers and food preparation workers.
The study, which compared 122 people with Alzheimer's to 235 who did not have the disease, was published Tuesday in the journal Neurology.
When both groups were in their 20s, they had jobs with similar mental demands, a level that was about 15 percent above the national average. However, as they grew older those who would later develop Alzheimer's tended to stay in jobs with about the same level of mental demands while those who did not get the disease tended to go into jobs with increasing mental demands.
As scientists now try to find ways to prevent the disease, a burning question is whether people can reduce their risk by staying mentally active throughout life.
"Not everybody can be an astrophysicist," said lead author Kathleen Smyth, a researcher at Case Western Reserve University. "(But) you want to keep your mind active. Some people call it novelty seeking ... things that get you thinking in a different way."
Smyth said even lower-end jobs can be made more mentally stimulating. And people can find ways to keep their minds active outside of work by playing games such as chess or crossword puzzles, playing a musical instrument, reading novels or taking an educational course.
However, there still is some uncertainty about exactly how a job or education affects a person's chances of getting Alzheimer's disease.
One explanation is that the disease process actually begins decades before symptoms appear and that a person simply starts to adapt by finding progressively less demanding activities over the years.
However, another possibility is that staying mentally active strengthens connections between neurons and builds a brain reserve, which may delay the onset of the disease.
"You really can't change your IQ, but this study underscores the protection of lifelong learning," said Diana Kerwin, an assistant professor of medicine and a geriatrics and dementia specialist with the Medical College of Wisconsin. "You can still have a manual labor job and overcome it by outside activities."
The concept of building a brain reserve also was bolstered by a 2003 study of 130 Catholic priests and nuns.
The study found that years of formal education, or something related to education, appeared to provide a type of cognitive reserve that reduced the harmful effect of plaques that build up in the brains of people with Alzheimer's.
The study's authors said it appeared that higher levels of education helped people tolerate the pathology of the disease.
A 2001 study found that leisure activity may reduce the risk of dementia regardless of a person's education or occupational background.
Those with high levels of leisure activity had a 38 percent lower risk of developing dementia, even when controlling for other risk factors, including ethnic background. Leisure activities included reading, going to movies, taking walks and talking with friends.
(c) 2004, Milwaukee Journal Sentinel. Distributed by Knight Ridder/Tribune News Service.