Background: Depression is commonly reported after coronary artery bypass grafting (CABG), and after cardiac surgery in general. Many earlier reports relied on non-standard assessments of depression, which may have overestimated its frequency. Cognitive decline has also been reported after CABG. We assessed the frequency of depression after CABG by a validated depression measure (Center for Epidemiological Study of Depression, CES-D), and examined the relation between depression and cognitive decline.
Methods: Patients were tested before CABG and 1 month and 1 year after surgery with a series of neuropsychological tests that assessed a range of cognitive areas. Depressed mood was measured by the CES-D scale, and defined as a score above 16.
Findings: 90 (73%) of the 124 patients were not depressed before surgery, and 34 were depressed at that time. Only 12 (13%) of patients not depressed before surgery were depressed at 1 month afterwards, whereas 18 (53%) of those who were depressed before surgery were depressed at 1 month (p < 0.001). 8 (9%) patients not depressed before surgery were depressed at 1 year; 16 (47%) of patients who were depressed before CABG were depressed at 1 year (p < 0.001). Statistical analysis showed only minimal correlation-or none at all-between depression and eight areas of cognitive outcome, or between changes in depressed status and cognitive scores.
Interpretation: Of those patients who were depressed after CABG, the large majority were depressed before surgery. There was no correlation, moreover, between depressed mood and cognitive decline after CABG, which suggests that depression alone cannot account for cognitive decline.