Compared with T2DM-nMCI subjects, the T2DM-MCI subjects had older age, higher percentage of having an ApoE ε4 allele (heterozygous), higher level of plasma Aβ1-42/Aβ1-40 ratio, higher platelet GSK-3β activity, and higher olfactory score that indicated decline of olfactory function (Table 1). The gene discussed is APOE; the disease is type 2 diabetes mellitus.