Marker or mediator? Is the link between anemia and outcomes in patients with coronary artery disease growing any clearer?

Continued advances in the medical and interventional management of coronary artery disease (CAD) have driven substantial improvements in long-term morbidity and mortality over recent years (1-3). However, the population of patients with chronic CAD has also grown older and more complex, and the burden of comorbidities among these patients also continues to rise. As clinicians strive to identify high-risk patients with the goal of further improving care, the prognostic impact of these non-cardiac conditions on patients’ outcomes has been highlighted by a host of publications. One common comorbidity, anemia, has been linked to poorer survival, greater rehospitalization rates, poorer physical function and reduced health-related quality-of-life (4-9). Whether present at presentation to the hospital or developing during hospital stays, anemia has been shown to increase short and long-term mortality and clinical event rates (8,10). These studies leave little doubt that anemia is a predictor of poor outcomes. The key translational questions, however, remain largely unanswered—is anemia a marker or a mediator of poor outcomes? Is there any targeted intervention to treat anemia, beyond standard therapy for coronary disease, that we can leverage improve outcomes for CAD patients with anemia?