Aging ApoE ε4 carriers with no sign of dementia have a diminished olfactory ability relative to noncarriers (Graves et al., 1999; Larsson et al., 2016; Olofsson et al., 2010), and in the ε4 carrier group, olfactory deficits are more strongly indicative of generalized cognitive decline in the coming years (Olofsson, Larsson et al., 2020; Olofsson et al., 2009). The gene discussed is APOE; the disease is Mental deterioration.