title: Executive function and depression as independent risk factors for postoperative delirium.
abstract: BACKGROUND
  Postoperative delirium has been associated with greater complications, medical cost, and increased mortality during hospitalization. Recent evidence suggests that preoperative executive dysfunction and depression may predict postoperative delirium; however, the combined effect of these risk factors remains unknown. This study examined the association among preoperative executive function, depressive symptoms, and established clinical predictors of postoperative delirium among 998 consecutive patients undergoing major noncardiac surgery.
  
  
  METHODS
  A total of 998 patients were screened for postoperative delirium (n = 998) using the Confusion Assessment Method as well as through retrospective chart review. Patients underwent cognitive, psychosocial, and medical assessments preoperatively. Executive function was assessed using the Concept Shifting Task, Letter-Digit Coding, and a modified Stroop Color Word Interference Test. Depression was assessed by the Beck Depression Inventory.
  
  
  RESULTS
  Preoperative executive dysfunction (P = 0.007) and greater levels of depressive symptoms (P = 0.049) were associated with a greater incidence of postoperative delirium, independent of other risk factors. Secondary analyses of cognitive performance demonstrated that the Stroop Color Word Interference Test, the executive task with the greatest complexity in this battery, was more strongly associated with postoperative delirium than simpler tests of executive function. Furthermore, patients exhibiting both executive dysfunction and clinically significant levels of depression were at greatest risk for developing delirium postoperatively.
  
  
  CONCLUSIONS
  Preoperative executive dysfunction and depressive symptoms are predictive of postoperative delirium among noncardiac surgical patients. Executive tasks with greater complexity are more strongly associated with postoperative delirium relative to tests of basic sequencing.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Division of Medical Psychology, Duke University Medical Center, Durham, North Carolina 27710, USA. smith562@mc.duke.edu
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Smith
authors.forename: Deborah K
authors.initials: DK
authors.lastname: Attix
authors.forename: B Craig
authors.initials: BC
authors.lastname: Weldon
authors.forename: Nathaniel H
authors.initials: NH
authors.lastname: Greene
authors.forename: Terri G
authors.initials: TG
authors.lastname: Monk