Imaging studies in AD populations repeatedly demonstrated possession of an APOE4 allele to be associated with more extensive atrophy in disease‐specific brain regions such as the medial temporal lobe 3, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, although this was not universal 24, 25. This evidence concerns the gene APOE and Alzheimer disease.