People with lower educational and lower occupational levels have at least a two times greater risk for developing Alzheimer's disease. The risk rises to three times as great when both low occupation and education occur together.
In a study published in the April 6,1994 issue of The Journal of the American Medical Association, National Institute on Aging (NIA) funded scientists at Columbia-Presbyterian Medical Center in New York City followed a population of 593 people, age 60 and above, for a 4 year period and observed Alzheimer's disease cases as they occurred. This study, because of its prospective nature, gives a greater validity to the education/occupation risk association than previous studies with similar results that were retrospective. "These findings are yet another piece in the puzzle of Alzheimer's disease, which today affects over 4 million Americans," according to HHS Secretary, Donna E. Shalala.
Principal investigator Dr. Yaakov Stern and his colleagues, Drs. Barry Gurland, Thomas Tatemichi, Ming Xin Tang, David Wilder and Richard Mayeux, hypothesize that higher occupational and educational backgrounds allow people to better cope with Alzheimer's for a longer time before symptoms actually present themselves. This "reserve hypothesis" is the one most favored on the basis of numerous analyses of the researchers' data.
The researchers administered yearly neuropsychological tests to residents living in the North Manhattan communities of Washington Heights and Inwood to see if anyone was beginning to exhibit signs of dementia. Other tests were given to assess levels of dementia as cases progressed, and test results were reviewed by a special panel to confirm the findings. At the end of the study, over 25 percent of the participants showed some sign of dementia. The researchers then analyzed their results on the basis of educational and occupational levels. Occupational levels were based on U.S. Census categories. Educational levels were measured from kindergarten through college, and a low level of education was set at 8 years of schooling. Setting these levels was crucial for the proper analysis and quantification of the investigators' findings since every added year of education showed a reduced risk of dementia.
Dr. Zaven Khatchaturian, Associate Director for Alzheimer's Disease Research at NIA, says, "This study gives us a great deal more information about certain psychosocial factors related to the disease. It is now even more clear that the cause of Alzheimer's is not any single factor, but rather a host of factors that interact in many ways in different people."
Investigators and caregivers will now have another factor to consider when trying to decide if failing memory and confusion are signs of Alzheimer's disease or some other, treatable problem. Dr. Stern says, "If some aspects of life experience can delay the onset of Alzheimer's disease for even a short time, the overall prevalence of the disease (amount in the population) will be reduced." This could lead to a large savings in health care costs and enhance the quality of life for many people. NIA analyses suggest that by reducing the onset of Alzheimer's disease by at least 5 years, the number of nursing home admissions for the disease could be significantly lowered.
The results of this prospective study confirm and extend an earlier slice-in-time study done in 1990 in Shanghai, China by NIA grantee, Dr. Robert Katzman of the University of California, San Diego. Dr. Katzman's study in Shanghai found that, as Dr. Stern discovered, a lower educational level was associated with a higher risk of Alzheimer's. This new study confirms the validity of Dr. Katzman's earlier observations and broadens our understanding of the extent to which education and occupation affect the likelihood of developing Alzheimer's.
NIA scientists are available to explain these findings and give a broad perspective on the research.
The National Institute on Aging is the major federal funding agency of Alzheimer's disease research. Please call (301) 496-1752 for further information and to arrange interviews.