In subjects with the APOE ε3/ε3 genotype, we did not document any associations between plasma apoE monomers or dimers, age, cognition, CSF AD biomarkers, CSF NfL, or sTREM2 levels (data not shown), whereas in ε3/ε4 subjects, plasma apoE3 homodimers were positively linked to age (Additional file 1: Table S8) and CSF NfL levels (Pearson’s (r) = 0.289, p = 0.054, n = 46), with the latter not reaching statistical significance. This evidence concerns the gene APOE and Alzheimer disease.