APOE and Mental deterioration: However, in line with other published reports (Devanand et al. 2015a, b; Schubert et al. 2008; Wilson et al. 2007), the present study also found that poor baseline olfactory identification alone predicted future cognitive decline (i.e. the effect of olfactory impairment on future cognitive decline is also present, albeit less pronounced, in ApoE-ε4 non-carriers).