African-Americans Develop Alzheimer Disease and Other Dementias at Twice the Rate of Africans
INDIANAPOLIS -- A 10-year study conducted in Indianapolis and Ibadan, Nigeria, has shown that African-Americans are twice as likely as Africans to develop dementia and Alzheimer disease.
 University College Hospital, Ibadan, Nigeria |
 Indianapolis-Ibadan Research Team in Ibadan |
 Dr. Adesola Ogunniyi, principal investigator, Nigeria |
This is the first report of incidence rate differences for Alzheimer disease and other dementias, contrasting populations from industrialized and non-industrialized countries, using the same group of investigators and identical methodologies. The study was conducted by researchers from the Indiana University School of Medicine and the University of Ibadan and published in the Feb.14 issue of the Journal of the American Medical Association.
"Since evaluation of dementia is subject to different interpretations, we felt it was crucial to have the same investigators evaluate both the American and Nigerian study subjects using the same clinical assessment instruments, which we designed specifically for this study," says Hugh Hendrie, M.B. Ch.B., principal author of the paper.
"These findings will allow us to pursue the elusive risk factors for Alzheimer disease in these two disparate populations," adds Dr. Hendrie, who, with IU School of Medicine and University of Ibadan colleagues has been studying the two groups since 1991.
The researchers previously published a prevalence study that indicated both dementia and Alzheimer disease were more prevalent in the Indianapolis African-American community than in the Yoruba community in Ibadan. Prevalence studies indicate how many cases of the diseases exist at one point in time. Incidence rates, which are the number of new cases occurring per year, are better indicators of true disease rates than prevalence studies because incidence studies are able to account for such factors as differing life spans.
Starting with the non-demented subjects from the prevalence study, the researchers conducted the newly published incidence study which for five years 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 the African-American group studied, 3.24 percent per year developed dementia, including 2.52 percent per year who developed Alzheimer disease.
In the African group, 1.35 percent per year developed dementia including 1.15 percent per year who developed Alzheimer disease. The majority of those who developed a dementing disorder, in either country, developed Alzheimer disease. In both communities two-thirds of the study subjects were female.
This study was funded by the National Institute on Aging, which also is supporting the next phase of the research, already underway. The new study will attempt to pinpoint the cause or causes of the significant disparity in rates of dementia and Alzheimer disease between the African-Americans and the Africans. Among the areas under consideration are factors that increase the risk of vascular diseases such as heart disease and stroke. Examples of these factors are hypertension, diabetes and high cholesterol levels. All are less prevalent in the African group than in the African-American one.
The researchers will further explore molecular genetic disparities between the two groups by building upon their previous work that showed a weak association between Alzheimer disease and a molecular variant of the ApoE gene in the Indianapolis group. This work revealed an even weaker association between the disease and ApoE in the Yoruba. ApoE has been linked to Alzheimer disease in other populations.
Additionally, the researchers plan to explore the impact of lifestyle and environmental factors, significantly different in the industrialized group and the non-industrialized group.
The JAMA study was authored by Dr. Hendrie, former chairman of the IU School of Medicine Department of Psychiatry; Adesola Ogunniyi, M.D., a neurologist at the University of Ibadan; Kathleen S. Hall, Ph.D., an IU School of Medicine epidemiologist; and nine others from the IU School of Medicine and the University of Ibadan. Dr. Hendrie also is affiliated with the IU Center for Aging Research and the Regenstrief Institute for Health Care.
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Video footage: Principal Nigerian Investigator Dr. Adesola Ogunniyi (pictured above) performs a neurological exam on Yoruban study participant Mrs. Ayisatu Laogun.
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