The association of anthocyanidins with Alzheimer’s dementia risk occurred only among those who were APOE-ɛ4 negative (Q4 vs. Q1: HR = 0.46, 95% CI = 0.29 to 0.73) and not in those without the allele (Q4 vs. Q1: HR = 1.5, 95% CI = 0.79 to 3.0). This evidence concerns the gene APOE and Alzheimer disease.