sMCI subjects were younger when compared to AD patients (p = 0.02), female prevalence was higher in HC than in sMCI (p = 0.001) and AD (p = 0.01), and APOE ε4 prevalence was lower in HC than in sMCI and AD, and higher in AD than in sMCI (all p values = 0.001). This evidence concerns the gene APOE and Alzheimer disease.