Neurological Foundation of New Zealand

The question: Is there a relationship between the jobs people do and their chances of getting Alzheimer's The test: People with and without the disease were compared, based on the mental, physical and social demands of the jobs they did in their 20s, 30s, 40s and 50s. 

The findings: Alzheimer's sufferers tended to be in jobs with low mental demands but higher physical demands.

The conclusion: Results fit the idea that mentally demanding jobs can affect chances of developing Alzheimer's.

However, it could be that the early influence of Alzheimer's reduces people's chances of working in mentally demanding jobs. New research supports the idea that keeping the brain busy can help stave off Alzheimer's disease. An American study recently reported by the Foundation’s affiliated organization, the American Academy of Neurology, has found that people who developed the disease tended to hold jobs with lower mental demands during their 30s, 40s and 50s than people who did not get Alzheimer's. 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 whose victims are expected to increase dramatically in the coming decades. Using the US Government forecasting method, the incidence of dementia in New Zealand is expected to rise from the present 40,000 to 100,000 by 2030. This study is the first to investigate the mental demands of employment over the course of several decades and link those demands to dementia diagnosis. An extensive US Department of Labour ranking of occupational demands was used to determine mental and physical job demands. Examples of jobs with high mental demands included engineering, medicine, science and maths teaching, architecture, computer programming and journalism.

Jobs with lower levels included porters, construction labourers, machine operators, assemblers and food preparation workers. The study compared 122 people with Alzheimer's with 235 who did not have the disease; when the participants in both groups were in their 20s, they had jobs with similar mental demands, a level that was about 15 per cent above the 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 demand 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, the question is whether people can reduce their risk by staying mentally active throughout life. Not everybody can be an astrophysicist, said the principal researcher, Dr Kathleen Smyth, of Case Western Reserve University School of Medicine in Cleveland, Ohio. The key ingredient is to keep your mind active. Even lower-end jobs could be made more mentally stimulating. The researchers don't know what the link is between AD and less mentally demanding occupations but there are several theories: 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, Dr Smyth added. There is also the possibility that jobs with higher mental 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.

One limitation of the study was that researchers did not control for socioeconomic status, Dr Smyth said. People with higher socio-economic status generally hold jobs with higher mental demands compared to those with lower socioeconomic status, she said. Therefore, variations in income, access to health care, better nutrition, and other factors related to socioeconomic status could be responsible in part for our findings. People could find ways to keep their minds active outside work by playing games such as chess or crossword puzzles, playing a musical instrument, reading novels or taking an educational course.

However, there was still some uncertainty about exactly how a job or education affects a person’s chances of getting Alzheimer's disease. One explanation was 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 was 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 Dr Diana Kerwin, a geriatrics and dementia specialist at the Medical College of Wisconsin.

You can still have a manual labour job and overcome it by outside activities. The concept of building a brain reserve was also 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 AD. The study demonstrated that higher levels of education appeared to help people tolerate the pathology of the disease. A 2001 study found that stimulating 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 per cent lower risk of developing dementia, even when controlling for other risk factors, including ethnic background.