Objective: To examine putative risk factors for incident Alzheimer’s Disease in the comparative epidemiological study of elderly African Americans in Indianapolis and Yoruba in Nigeria.
Design: The samples of subjects aged 65 years and older were drawn from community dwelling African Americans living in Indianapolis, and Yoruba living in Ibadan, Nigeria. As reported earlier by us, the age standardized annual incidence rate for Alzheimer’s disease is significantly higher in the African Americans (2.52% [95%CI, 1.40%-3.64%]) compared to the Yoruba (1.15% [95%CI, 0.96%-1.35%]) (1).
Materials and Methods: Information about demographic characteristics, medical history, and lifestyle was collected from 2212 Indianapolis subjects and 2,486 Ibadan subjects using the Community Screening Interview for Dementia in the baseline prevalence study (1992-’93). Of these, 498 subjects in Indianapolis and 530 subjects in Ibadan were given clinical assessments and diagnosed in two follow up incidence waves (1994-’95, 1997-’98). Putative risk factors for AD were analyzed univariately using t-tests and chi-square tests, and multivariately with stepwise logistic regression.
Results: A total of 89 cases of AD were diagnosed in Indianapolis and 62 in Ibadan for the two incidence follow ups. A total of 381 subjects were diagnosed as not demented in Indianapolis and 460 were not demented in Ibadan. Age at diagnosis was a significant risk factor in both sites. In Ibadan female gender was significant, and Indianapolis childhood rural residence was significant.
Conclusion: While advanced age seems to constitute a risk for AD across cultural boundaries, there may be environmental risk factors that bear differential associations with gender or residence in our study sites.
1. Hendrie, H.; Ogunniyi, A.; Hall, K. et al. Incidence of Dementia and Alzheimer Disease in 2 Communities: Yoruba residing in Ibadan, Nigeria, and African Americans residing in Indianapolis, Indiana. JAMA 2001;285 #6:739-747.
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