According to the study, people with Alzheimer's are more likely to have had less mentally stimulating careers than their peers who do not have Alzheimer's. The research team, led by Kathleen Smyth, PhD, and Robert Friedland, MD, of the University Memory and Aging Center, studied 122 people with Alzheimer's and 235 people without the disease, all of whom were more than 60 years old. They gathered information about their occupational history over 40 years, from ages 20 through 60.
"We didn't simply classify study subjects as blue collar or white collar," said Dr. Smyth. "We drilled down further into occupational tasks, to classify a job as mentally stimulating based on its complexity, variety of tasks, whether it involved creative thinking or manipulation of data. Less mentally demanding jobs included more routine and monotonous tasks."
The most intriguing finding was that the mental demands of occupations during the decade of the 20's did not appear linked to later development of Alzheimer's. But starting in their 30's, those people who did not develop Alzheimer's were found to have jobs that were more mentally stimulating than those who did develop Alzheimer's later in life. And that difference in occupational experiences in the two groups persisted during their 40's and 50's.
"It could be that the disease has a very early effect on the individual's capacity to pursue a mentally challenging occupation," said Dr. Smyth. "Or, it could be that higher levels of mental demands result in increased brain cell activity, which may help maintain a 'reserve' of brain cells that resists the effects of Alzheimer's. There is also the possibility that jobs with higher demands require skills that enhance an individual's ability to perform well on the tests used to diagnose Alzheimer's. If this is the case, then the disease may go undetected in these people until the disease is much farther along than in those whose jobs pose lower mental demands."
These findings are consistent with earlier studies presented by the Case/University Hospitals of Cleveland research team. Dr. Robert Friedland and the research team previously studied the link between leisure activities like playing chess, reading books, learning an instrument or a new language. They found that people who were free of Alzheimer's disease in later life were more likely to have engaged in mentally stimulating leisure activities when they were younger. "It is important to recognize the link between Alzheimer's and daily life activities that are under our control," said Dr. Friedland. Other lifestyle factors influencing the risk include diet and physical activity.
The current study reported in Neurology did not control for socioeconomic status, and environmental demands and exposures of occupations, but did control for educational levels of participants. The research was supported by grants from the National Institutes of Health, the Fullerton Family Foundation, Mandel Foundation, Nickman family, Philip Morris, USA, and the American Physicians Fellowship for Medicine in Israel.