Postoperative delirium (POD) is a common problem among elders who undergo surgery and anesthesia, with major health consequences. This investigation is expected to clarify and understand the role of neurocognitive reserve in the occurrence of POD, provide grounds to preoperative cognitive risk stratification and early preventive interventions to improve patients' outcomes. The surgical procedure and anesthesia are stressor events that interact with underlying risk factors and play an important role in the development of POD. Evidence is lacking to make recommendations on anesthesia related perioperative interventions. This investigation will contribute to better understand the association between types of anesthesia, medications, monitoring and other anesthesia related factors that can be a target for preventive interventions. This research will add knowledge and clarify the role of predictors and precipitant factors that might enlighten future research on risk stratification models and interventions, prognostic significance, and treatment implications for POD.