(Montagne et al. [64] have since shown that in APOE-ε4 carriers, blood-brain-barrier breakdown occurs in the hippocampus and medial temporal lobe in cognitively unimpaired carriers but breakdown is greater in cognitively impaired subjects, and is unrelated to CSF or PET measurements of Aβ or tau pathology; they suggest that the breakdown contributes to APOE-ε4-associated cognitive decline, independently of Alzheimer’s disease pathology). Here, APOE is linked to Alzheimer disease.