To the Editor.
—It has recently been found that the frequency of the E4 allele of apolipoprotein E (apo E) is increased (about threefold) in familial and sporadic late-onset Alzheimer's disease (AD).1 Apolipoprotein E is encoded by a single gene on chromosome 19; a common polymorphism is determined by alleles E2, E3, and E4. The frequency of apo E E4 is around 0.10 to 0.16 in the general elderly population, and 0.36 to 0.48 in late-onset AD patients. This observation has given rise to a number of ethical and scientific questions regarding the necessity and meaning of apo E phenotyping in the general population. However, the specificity of risk is unknown.We assessed the frequency of apo E alleles in 87 AD and 21 vascular dementia patients and in 51 elderly hyperlipidemic nondemented controls. Diagnosis of probable AD (Mini-Mental State Examination score, 10.4 [SD,
Frisoni GB, Bianchetti A, Govoni S, Trabucchi M, Calabresi L, Franceschini G. Association of Apolipoprotein E E4 With Vascular Dementia. JAMA. 1994;271(17):1317. doi:10.1001/jama.1994.03510410029016