Polymorphisms in specific genes, such as APOE, cystatin C (CST3), cholesterol 24-hydroxylase (CYP46) (8), and phosphatidylinositol-binding clathrin assembly protein gene (PICALM) (9), may be associated with the risk of development of MCI due to AD or AD itself. Here, CYP46A1 is linked to Alzheimer disease.