Besides, six ApoE genotypes including ε2ε2, ε3ε3, ε4ε4, ε2ε3, ε2ε4, and ε3ε4 were detected in included patients, showing that the prevalence of ε3ε4 genotype was higher while ε3ε3 was lower in T2DM-MCI group. Here, APOE is linked to type 2 diabetes mellitus.