Overall, the APOE ε4 allele frequency was 12.5 % (16/128 alleles), and was not significantly different in MND (10.7 %, 6/56 alleles), FTD + MND (13.3 %, 4/30 alleles) or FTD (13.6 %, 6/44 alleles (χ2 = 0.232, p = 0.890), although the APOE ε4 allele frequency in those patients with MND, FTD + MND and FTD, collectively, showing amyloid plaque formation (20 %, 8/40 alleles) tended to be significantly greater (χ2 = 3.17, p = 0.075) than in those without amyloid (8.9 %, 8/90 alleles). Here, APOE is linked to mild neurocognitive disorder.