Using a cumulative genetic risk score for T2DM (polygenic score for T2DM) as a valid instrument, we observed a positive but non-causal association between history of T2DM and CIND in the European ancestry (OR = 1.30, 95% CI: 1.10, 1.52), after adjusting for age, sex, years of education, APOE-ε4 allele status, and five ancestry-specific PCs. Here, APOE is linked to type 2 diabetes mellitus.