GSTM1 and Hypoalbuminemia: Low pre-operative Hb concentrations [p = 0.026, odds ratio (OR) = 0.978, 95% CI = 0.959–0.997] and change in perioperative Hb concentration (p = 0.006, OR = 1.033, 95% CI = 1.010–1.057) together were significantly associated with POD after adjustment for age, stroke history, surgery and anesthesia type, hypoalbuminemia (pre-operatively and post-operatively), midazolam use, intraoperative blood loss, operation and anesthesia time, post-operative ICU transfer and hypoxemia, and the VAS score within post-operative 3 days (Table 3).