Association of Metformin Use on Postoperative Delirium Risk in Patients with Type 2 Diabetes: A Retrospective Cohort Study

Aim Metformin has been reported to improve age-related diseases, including dementia. Prior studies have suggested that metformin use is associated with a decreased risk of delirium. This study aimed to analyze the medical records of surgical patients with comorbid type 2 diabetes to evaluate the relationship between metformin and both postoperative delirium. Method A retrospective cohort study of patients diagnosed with type 2 diabetes who underwent surgery for malignancy in the Departments of Gastrointestinal Surgery and Thoracic Surgery was conducted. A total of 1,159 patients were analyzed to examine metformin use and the incidence of delirium. Results Among the 1,159 patients, 1,026 were classified as the non-metformin-treated diabetes group and 133 as the metformin-treated diabetes group. The incidence of delirium was 17.0% in the non-metformin-treated group and 15.0% in the metformin-treated group. Metformin use was not associated with a reduced risk of delirium after adjustment for confounding factors (Relative risk: 0.94, 95% confidence interval [CI], 0.60~1.45, p = 0.766). The propensity score weighting analyses showed no significant association between metformin use and the incidence of postoperative delirium (Relative risk: 1.51, 95% CI, 0.62~3.69, p = 0.370). Conclusion In this study, metformin use was not significantly associated with postoperative delirium.