APOE and Alzheimer disease: In this study, we analyzed in detail the impact of ApoE4 allele frequency on CSF concentrations of AD core biomarkers (Aβ 42, t-tau and p-tau) cross-sectionally and on progression of decline in a cohort of MCI subjects from the Dementia Competence Network, stratified into 3 groups: MCI-stable individuals, MCI-AD progressors and MCI subjects progressing to other forms of dementia.