ApoE4’s association with reduced cerebral glucose metabolism has been observed in both AD patients and non-demented individuals of the same age, a phenomenon that precedes cognitive symptoms by decades and likely occurs before extensive Aβ accumulation (Hirono et al., 2002; Mosconi et al., 2004; Reiman et al., 2004; Reiman et al., 2005; Small, 2001; Small et al., 2004; Scarmeas et al., 2005). The gene discussed is APOE; the disease is Alzheimer disease.