title: Apolipoprotein E: risk factor for Alzheimer disease.
abstract: The apolipoprotein E gene (APOE) has three common alleles (epsilon 2, epsilon 3, and epsilon 4) that determine six genotypes in the general population. In this study, we examined 77 patients with late-onset Alzheimer disease (AD), along with an equal number of age- and sex-matched controls, for an association with the APOE-epsilon 4 allele. We show that the frequency of this allele among AD patients was significantly higher than that among the control population (.351 vs. .130, P = .000006). The genotype frequencies also differed between the two groups (P = .0002), with the APOE-epsilon 4/epsilon 3 genotype being the most common in the AD group and the APOE-epsilon 3/epsilon 3 being the most common in the control group. In the AD group, homozygosity for epsilon 4 was found in nine individuals, whereas none was found in the control group. The odds ratio for AD, when associated with one or two epsilon 4 alleles, was 4.6 (95% confidence interval [CI] 1.9-12.3), while the odds ratio for AD, when associated with heterozygosity for APOE-epsilon 4, was 3.6 (95% CI 1.5-9.8). Finally, the median age at onset among the AD patients decreased from 83 to 78 to 74 years as the number of APOE-epsilon 4 alleles increased from 0 to 1 to 2, respectively (test for trend, P = .001). Our data, which are in agreement with recent reports, suggest that the APOE-epsilon 4 allele is associated with AD and that this allelic variant may be an important risk factor for susceptibility to AD in the general population.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905.
authors.forename: M S
authors.initials: MS
authors.lastname: Tsai
authors.forename: E G
authors.initials: EG
authors.lastname: Tangalos
authors.forename: R C
authors.initials: RC
authors.lastname: Petersen
authors.forename: G E
authors.initials: GE
authors.lastname: Smith
authors.forename: D J
authors.initials: DJ
authors.lastname: Schaid
authors.forename: E
authors.initials: E
authors.lastname: Kokmen
authors.forename: R J
authors.initials: RJ
authors.lastname: Ivnik
authors.forename: S N
authors.initials: SN
authors.lastname: Thibodeau
mesh_terms: D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000544:Alzheimer Disease / Q000235:genetics*; D053327:Apolipoprotein E4; D001057:Apolipoproteins E / Q000235:genetics*; D001483:Base Sequence; D016022:Case-Control Studies; D005260:Female; D005787:Gene Frequency; D005796:Genes; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D016015:Logistic Models; D008297:Male; D008969:Molecular Sequence Data; D016017:Odds Ratio; D012307:Risk Factors; D017422:Sequence Analysis, DNA
chemical_list: D053327:Apolipoprotein E4; D001057:Apolipoproteins E