The association between white blood cell count and acute myocardial infarction mortality in patients ≥65 years of age: findings from the cooperative cardiovascular project

OBJECTIVES The purpose of the study was to examine the association between white blood cell (WBC) count on admission and 30-day mortality in patients with acute myocardial infarction (AMI). BACKGROUND Elevations in WBC count have been associated with the development of AMI and with long-term mortality in patients with coronary artery disease. However, the relationship between WBC count and prognosis following AMI is less clear. METHODS Using the Cooperative Cardiovascular Project database, we evaluated 153,213 patients ≥65 years of age admitted with AMI. RESULTS An increasing WBC count is associated with a significantly higher risk of in-hospital events, in-hospital mortality and 30-day mortality. Relative to those patients in the lowest quintile, patients in the highest quintile were three times more likely to die at 30 days (10.3% vs. 32.3%; p < 0.001). After adjustment for confounding factors, WBC count was found to be a strong independent predictor of 30-day mortality (odds RATIO = 2.37; 95% confidence interval 2.25 to 2.49, P = 0.0001 for the highest quintile of WBC count). CONCLUSIONS White blood cell count within 24 h of admission for an AMI is a strong and independent predictor of in-hospital and 30-day mortality as well as in-hospital clinical events. Although the mechanism of the association remains speculative, the results of this study have important clinical implications for risk-stratifying patients with AMI.