ApoE4 has been associated with increased cholesterol levels in both blood (Corder et al., 1993; Notkola et al., 1998) and CSF, as measured by the metabolite 24S-hydroxycholesterol, in AD patients (Papassotiropoulos et al., 2002; Leoni et al., 2006). This evidence concerns the gene APOE and Alzheimer disease.