Is depression after an acute coronary syndrome simply a marker of known prognostic factors for mortality?

OBJECTIVE Controversy remains over whether the association between depression and mortality in patients with acute coronary syndrome (ACS) is confounded by incomplete adjustment for measures of known prognostic markers. We assessed a) whether depression was associated with the most comprehensive empirically derived index of clinical mortality predictors: the Global Registry of Acute Coronary Events (GRACE) risk score for predicting 6-month mortality after discharge for ACS; and b) whether depression remained an independent predictor of all-cause mortality after adjustment for the GRACE score and left ventricular dysfunction. METHODS We surveyed prospectively 457 patients with ACS (aged 25-92 years; 41% women, 13% black, and 11% Hispanic), hospitalized between May 2003 and June 2005. Depressive symptoms were assessed with the Beck Depression Inventory (BDI) and diagnosis of major depressive disorder (MDD) was made by a structured psychiatric interview, within 1 week of hospitalization. RESULTS Despite differences in individual components of the GRACE score between depressed and nondepressed participants, neither depression measure was associated with overall GRACE score. For participants with MDD, the mean +/- standard deviation GRACE score was 84 +/- 33, compared with 92 +/- 31 for those without MDD (p = .09). Using Cox proportional hazards regression analysis, MDD and depressive symptom severity each predicted mortality after controlling for GRACE score and left ventricular dysfunction (adjusted hazard ratio for MDD = 2.51; 95% Confidence Interval = 1.45-4.37). CONCLUSION Depression is not simply a marker of clinical indicators that predict all-cause mortality after ACS. This strengthens the assertion that there is something unique in the association between depression and post-ACS prognosis, independent of known prognostic markers.