APOE and Alzheimer disease: This difference provided significance for recessive analysis (comparing CC + CT vs TT) of the differences between AD APOE ε4 non-carriers and AD APOE ε4 carriers (χ2 = 6.317, df = 1, P = 0.012), though not for analyses of allele frequencies (χ2 = 0.429, df = 1, P = 0.513).