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African-Americans Twice as Likely as Africans to Develop Alzheimer Disease

A 10-year study conducted in Indianapolis and Ibadan, Nigeria indicates that African-Americans are twice as likely as Africans to develop Alzheimer disease and other dementias.

Researchers from the Indiana University School of Medicine, Indianapolis, and the University of Ibadan, Nigeria, followed 2,147 African Americans in Indianapolis and 2,459 Yoruba in Ibadan, age 65 and older, to see if they developed dementia and Alzheimer disease. In both locales, two-thirds of the study subjects were female.

Of the African-American subjects, 3.24% per year developed dementia, including 2.52% per year who developed Alzheimer disease. Only 1.35% of the African subjects developed dementia including 1.15% per year who developed Alzheimer disease.

“These findings will allow us to pursue the elusive risk factors for Alzheimer disease in these two disparate populations,” explains Hugh Hendrie, MB, ChB, a researcher at the Department of Psychiatry, IU School of Medicine and principal author of the paper, which appeared in the February 14 issue of the Journal of the American Medical Association (JAMA).

Hendrie established a partnership with Benjamin Osuntokun of the University of Ibadan, Nigeria to form the Indianapolis-Ibadan Dementia Project. Their goal was to search for environmental, potentially modifiable, risk factors for Alzheimer’s disease by studying two populations now living in very different environments: African Americans living in Indianapolis and Yoruba Nigerians living in Ibadan. The project resulted in several important findings, which suggest that there may be environmental risk factors for the development of Alzheimer’s disease.

Although studies of Alzheimer disease prevalence among racial and ethnic groups has indicated that the risk is higher for African Americans and Hispanics than it is for whites, there have been no conclusive results. Nevertheless, the differences are important to study because of the growing percentage of non-whites in the older U.S. population. According to the 1999 Progress Report by the National Institute on Aging/National Institutes of Health (NIA/NIH), by the year 2050, the percentage of the population over the age of 85 that is non-Caucasian will have increased from 16% to 34%.

The NIA funded the study and is also supporting the next phase of the research, which is already underway. This new study will attempt to discover the cause or causes of the disparity between African Americans and Africans contracting dementia and Alzheimer disease. Factors under consideration include hypertension, diabetes and high cholesterol levels. The African group suffers less from all three of these than do African Americans.

The researchers will continue to explore the molecular genetic disparities between the two groups, including the association between Alzheimer disease and a molecular variant of the ApoE gene. Previous research had shown that the Yoruba subjects experienced a weaker association between the disease and the gene than did the Indianapolis group.

They also plan to explore the impact of lifestyle and environmental factors, which are significantly different between the industrialized and non-industrialized groups.

“The reason to choose populations from a developing and a developed country is to increase the possibility of environmental diversity,” says Hendrie. “It is hoped that this report will encourage more research into Alzheimer’s in these countries.”