GSTM1 and delirium: Univariate analysis showed that age > 75 years, history of stroke, preoperative albumin ≤ 35 g/L, preoperative Hb ≤ 100 g/L, preoperative PaO2 ≤ 60 mmHg, and time between admission to surgery > 3 days, were risk factors of postoperative delirium (Table 1).