APOE and frontotemporal dementia: Age and APOE ɛ4 allele accelerating pathogenic Aβ-42 brain deposition starting in late middle age in persons with normal cognition are causing decrease of CSF Aβ-42 but not the Aβ-40 concentration [150], while CSF Aβ-40 levels in frontotemporal dementia (FTD) are decreased [151] and fluctuations of CSF Aβ levels have been found in individual subjects [152].