Consistent accumulating evidence further shows that APOE ε4 carriers devoid of cognitive symptoms exhibit low cerebral metabolic rate of glucose (CMRgl) in the posterior cingulate, precuneus, parietotemporal and frontal regions [9–13], and reduced regional gray matter volume (GMV) in the hippocampus [14] and amygdala [15], all brain regions known to be affected in AD. Here, APOE is linked to Alzheimer disease.