The demographic and clinical characteristics of the enrolled elderly patients were exhibited in Table 1 in detail. 39 of the 160 patients had suffered POD with a POD incidence of 24.4%, which was similar to other previous studies . The mean age of all the enrolled patients was 70.1 years, and significant difference in age between the patients with or without POD was found. The preoperative MCCI score was significantly higher in patients who suffered POD when compared with those without POD. In addition, the preoperative MMSE score and percentage of heavy drinkers were significantly higher in the delirious group than the nondelirious group. No statistically significant differences were found in the gender, education, body mass index, smoking habits, and ASA physical status between the patients with POD or not.