Age (OR = 1.083, 95%CI = 1.024-1.146), education level (OR = 0.869, 95%CI = 0.776-0.973), preoperative K concentration (OR = 4.453, 95%CI = 1.331-14.897), preoperative Hb (OR = 0.903, 95%CI = 0.816-0.999), and anemia (OR = 0.387, 95%CI = 0.171-0.873) were significantly correlated with POCD occurrence in 3 months after operation (P = 0.006, 0.015, 0.015, 0.047, and 0.022, respectively). Here, GSTM1 is linked to anemia (phenotype).