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| |  Genetic Risk for Alzheimer's in Caucasians Also Present in African Americans TALLAHASSEE, Fla. -- June 19, 2008 -- A commonly recognised gene that places one at risk for Alzheimer's disease does not discriminate between African Americans and Caucasians, according to new research led by Florida State University. Natalie Sachs-Ericsson, MD, Florida State University, Tallahassee, Florida, and graduate student Kathryn Sawyer have found that the gene apolipoprotein E (APOE) epsilon 4 allele is a risk factor for African Americans as well as Caucasians. Until now, it has been a mainstream belief that the gene is only a risk factor for Caucasians. Dr. Sachs-Ericsson's team theorised that small sample sizes coupled with possible racial bias in measuring cognitive functioning may explain why some studies have failed to detect the effect of the APOE epsilon 4 allele on cognitive decline among African Americans. In addition, false-positive rates for dementia on standardised screening tests are higher for African Americans compared with Caucasians when compared with neurologists' ratings of cognitive status, Dr. Sachs-Ericsson said. And those false positives may have obscured the influence of the gene on dementia. The researchers used data from the Duke Established Populations for Epidemiologic Studies of the Elderly (EPESE). To determine genotype, DNA samples were collected through blood or cheek swabs from 2,076 people aged 65 years or older. Participants were divided into 2 groups: those who had at least 1 APOE epsilon 4 allele and those who had no epsilon 4 allele. Cognitive errors on a standardised test were measured in 4 in-person interviews over a 10-year period ending in 1997. Those with the epsilon 4 allele -- both African Americans and Caucasians -- made increasingly more cognitive errors over time on a questionnaire that assessed knowledge of items such as the day, date, and current president compared with those without the gene. "While having the APOE epsilon 4 allele increases the risk of developing Alzheimer's disease, APOE genotype alone is not enough to predict the disease," Dr. Sachs-Ericsson said. "We don't understand why the allele predicts Alzheimer's in some but not others. There may be other biological or genetic causes or even environmental factors, such as diet, that determine whether the allele will lead to Alzheimer's. We need a better understanding of what these factors are and whether they affect African Americans and Caucasians equally." "The results of our study have clear implications for research and treatment of Alzheimer's disease," Dr. Sachs-Ericsson said. "The APOE test might be used as 1 tool in identifying people who are at risk for Alzheimer's. We now know that African Americans and Caucasians alike need to be considered for such risk assessments." The researchers' findings underscore the importance of including both African Americans and Caucasians in future studies that explore why the APOE genotype is a risk factor for Alzheimer's disease. By understanding the mechanism by which the genotype confers risk, scientists could potentially develop medicines that slow the progress of Alzheimer's or even prevent it, according to Dr. Sachs-Ericsson.
SOURCE: University of Florida
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