The MMSE score was significantly correlated with age (r = − 0.442, p < 0.001), BMI (r = 0.134, p = 0.014), education years (r = 0.338 p < 0.001), apolipoprotein A1/apolipoprotein B ratio (r = − 0.109, p = 0.046), and glycated hemoglobin (r = − 0.235, p < 0.001) in patients with T2DM. Here, APOB is linked to type 2 diabetes mellitus.