APOE and Alzheimer disease: Analysis of AD related biomarkers in the CSF indicates significantly decreased Aβ42 levels among the APOE ε3ε4 carriers compared to APOE ε3ε3 carriers (Fig. 4E) but no differences in the levels of P-Tau181 or total Tau between the genotypes (Additional file 1, Fig. S3 A-D).