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November 18, 1998

The APOE-∊4 Allele and Alzheimer Disease Among African Americans, Hispanics, and Whites—Reply

Author Affiliations

Margaret A.WinkerMD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Senior EditorIndividualAuthor

JAMA. 1998;280(19):1661-1663. doi:10-1001/pubs.JAMA-ISSN-0098-7484-280-19-jbk1118

In Reply.—Dr Barker and colleagues suggest that recruitment methods might explain differences in the association between AD and the APOE-∊4 polymorphism reported by us compared with other studies. However, studying clinic patients can result in a form of bias, referred to as Neyman's fallacy,1 such that the relationship between a risk factor and disease is different for those who participate (self-selected cases, specialty clinic or hospital cases, or prevalent cases) than for individuals who would have been eligible to participate but were otherwise not in the study.1 Because prevalence is the product of incidence multiplied by duration, risk factors identified in prevalent cases may reflect factors that promote survival with the disease. Indeed, the mortality rate among patients with AD may be lower among patients with an APOE-∊4 allele.2,3