Introduction: Postoperative delirium (POD) is a sudden and usually temporary cognitive and emotional disorder, common in older patients submitted to surgery. This is an underdiagnosed, undertreated and still poorly understood condition. This review aims to identify the prevalence and risk factors for POD in order to improve preventive and treatment measures for this condition. 
Method: A qualitative systematic review of the literature was conducted in the MEDLINE database. Prospective studies published since 2012 and evaluating the incidence of postoperative delirium (determined through the Confusion Assessment Method) and its risk factors were selected. Patients with 65 years of age or higher submitted to non-cardiovascular surgery were enrolled. Search terms included “postoperative delirium” in the title. 
Result: Of the 194 results retrieved, 10 were considered eligible (4116 patients). POD rates changed between 8.5% and 47.5% (weighted mean=28.6%). Weighted mean POD incidence was higher in urologic studies (37.1%), compared to orthopedic studies (32.2%) and others (22.1%). Patient-specific factors related to POD incidence included increased age, history of cognitive and emotional/affective impairment and higher functional dependence. Preoperative anemia, intraoperative hemodynamic complications and transfusion were other risk factors commonly reported. 
Conclusions: POD is a prevalent complication in several surgical settings. Adequate preoperative assessment of the patient understanding of key surgical variables that may predispose to this condition is paramount for proper prevention and treatment.

Postoperative delirium in non-cardiac surgery: systematic review of incidence and risk factors