Cognitive dysfunction after coronary artery bypass surgery: a case-controlled study.

Twenty-two patients screened from a sample of 391 having coronary artery bypass grafting (CABG) showed significant declines on the Mini-Mental State Examination (MMSE) administered preoperatively and four days postoperatively. The MMSE is a 30-point cognitive function screening instrument for dementia and delirium. These patients were compared with 22 matched control subjects who exhibited intact cognitive function postoperatively. The study assessed the association between postoperative cognitive dysfunction and socioeconomic status, potential effects of selected surgical/anesthetic factors, and preoperative anxiety and depression (Zung Anxiety and Center for Epidemiologic Studies-Depression [CES-D] self-rating scales). The results indicate that a higher preoperative level of depression reported on the CES-D (mean score of study patients 22.1 versus 12.7 for controls) is significantly associated with the development of postoperative cognitive dysfunction (P less than .01). The educational and occupational levels of study patients were significantly below those of controls (P less than .01, P less than .02). Occurrence of a postoperative complication was the only surgical/anesthetic factor found to be significantly associated with cognitive dysfunction (P less than .01). These findings suggest that preoperative depression significantly increases the risk for immediate postoperative cognitive dysfunction, and that lower socioeconomic status may confer greater risk for postoperative cognitive morbidity.