Margaret A.WinkerMD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Senior EditorIndividualAuthor
To the Editor.—Dr Farrer and colleagues1 provide evidence for a strong association between
APOE polymorphisms and Alzheimer disease (AD) risk in Caucasian and Japanese
populations. In contrast, the combined ORs for AD in African Americans with
all genotypes (other than 2 ∊4 alleles) were not significantly different
from 1.0. The authors attributed the weak APOE∊4–AD
association in African Americans to differences in study design with variable
demographic characteristics, sampling strategies, and degrees of diagnostic
consistency. Another possible explanation is that the presence of a single ∊4
allele was an AD risk factor in some African Americans and not in others.
Such a variable pattern of association can be obscured when studied with small
samples that are combined in a meta-analysis.
Shadlen M. Effects of Age and Ethnicity on the Link Between APOE ∊4 and Alzheimer Disease. JAMA. 1998;279(8):580-582. doi:10-1001/pubs.JAMA-ISSN-0098-7484-279-8-jbk0225