Indianapolis Ibadan Epidemiological Study of Dementia
The Indianapolis-Ibadan Dementia Project, established in 1991, is a longitudinal, prospective population-based comparative epidemiological study of the prevalence and incidence rates and risk factors for Alzheimer's disease and other age associated dementias. The project enrolled community-dwelling elderly (age > 65 years) African Americans living in Indianapolis and Yoruba living in Ibadan, Nigeria, employing the same research design, methods, and investigators. It initially reported significantly lower prevalence rates of disorders in the Yoruba compared to the African Americans. In subsequent waves of the study (1994-1995, 1997-1998) incidence rates, rates of newly diagnosed cases, were also found to be significantly lower in the Yoruba. In genetic studies, the frequency of the APOE ε4 allele was about the same in the two groups, but there was a differential effect of APOE ε4 on Alzheimer’s disease risk between the two cohorts with the APOEe4 risk being much weaker in Yoruba. A major conclusion of the study was that the environment, particularly factors which increased risk for cardiovascular disease also play a major role in the etiology of dementia/Alzheimer Disease and are potentially preventable. More than 100 papers have been published in major journals during the past two decades using data from this study. A complete list of references, together with a summary of our research design and results, is included on the Publications page.
Genome wide association study analyses for African Americans are being conducted in collaboration with Dr. Denis Evans of Rush University in Chicago and Dr. Phillip De Jager at the Broad Institute in Cambridge. In April 2011 the project was approved for a genome wide association analysis for the Yoruba carried out by the Center for Inherited Diseases Research at Johns Hopkins. The project has collaborative relationships with several external investigators.
The Indianapolis Ibadan Dementia Project was funded through a grant from the National Institute on Aging R01AG009956.
The funding for this study ended in 2012. During the course of the study a massive data set involving over 8000 (n=8528) elderly African American and Yoruba participants over a 20 year period was collected. This also included the collection of blood samples and DNA at the 2001 assessment wave (1516 African Americans and 1254 Yoruba). A description of the data set is included in the website.
The availability of these data has generated considerable interest in the scientific community. The bio specimens are now housed at the National Cell Repository for Alzheimer Disease (NCRAD Tatiana Foroud PI). As described above, Genome Wide Association Studies (GWAS) were conducted on the DNA samples. The results from these analyses for Yoruba, with limited phenotypic data, is available on the NCBI website data base for genotypes and phenotypes (dbGAP). The African American GWAS data is part of the analysis of the Alzheimer Disease Genetic Consortium (Gerard Schellenberg PI), and genetic and limited phenotypic data for both African American and Yoruba participants is included in the NIA sponsored website National Institute on Aging Genetics of Alzheimer’s Disease Data Storage (NIAGADS).
Analysis of the data continues; see Data Resources. A study linking the African American data with electronic medical records, titled Longitudinal Interactive vascular exposure and Alzheimer Disease, (PI Su Gao) is funded by NIA (RO1 AG 045350). Other secondary analyses projects are currently being explored.
Instruments which were developed during the course of the study and are described in the website are still widely used in international studies.