Association of Chronic Kidney Disease and Anemia with Physical Capacity

Chronic kidney disease (CKD) and anemia are common conditions in the outpatient setting, but their independent and additive effects on physical capacity have not been well characterized. The association of CKD and anemia with self-reported physical function was evaluated and exercise capacity was measured in patients with coronary disease. A cross-sectional study of 954 outpatients enrolled in the Heart and Soul study was performed. CKD was defined as a measured creatinine clearance <60 ml/min, and anemia was defined as a hemoglobin level of <12g/dl. Physical function was self-assessed using the physical limitation subscale of the Seattle Angina Questionnaire (0 to 100), and exercise capacity was defined as metabolic equivalent tasks achieved at peak exercise. In unadjusted analyses, CKD was associated with lower self-reported physical function (67.6 versus 74.9; P < 0.001) and lower exercise capacity (5.5 versus 7.9; P < 0.001). Similarly, anemia was associated with lower self-reported physical function (62.6 versus 74.3; P < 0.001) and exercise capacity (5.7 versus 7.5; P < 0.001). After multivariate adjustment, CKD (69.4 versus 74.2; P = 0.003) and anemia (67.5 versus 73.6; P = 0.009) each remained associated with lower mean self-reported physical function. In addition, patients with CKD (6.3 versus 7.7; P < 0.001) or anemia (6.5 versus 7.4; P = 0.004) had lower adjusted mean exercise capacities. Participants with both CKD and anemia had lower self-reported physical function and exercise capacity than those with either alone. CKD and anemia are independently associated with physical limitation and reduced exercise capacity in outpatients with coronary disease, and these effects are additive. The broad impact of these disease conditions merits further study.