Cardiorespiratory Fitness and Mortality in Patients With Chronic Kidney Disease: A Prospective Cohort Study

Objective: To assess the association between objectively measured cardiorespiratory fitness (CRF) and mortality in patients with chronic kidney disease (CKD). Patients and Methods: From a large cohort of US veterans (n=750,302) based on the ETHOS (Exercise Testing and Health Outcomes) study, we identified 45,674 men and women aged 30 to 95 years (mean, 65.1 ± 8.8 years) who completed an exercise treadmill test (ETT) within the Veterans Affairs hospitals across the United States. All were diagnosed with CKD before the ETT by International Classification of Diseases 9^th and 10^th revision codes. Age- and-sex-specific CRF categories (quintiles) were established based on peak metabolic equivalents (METs) achieved during the ETT. We computed HRs and 95% CIs with Cox regression analyses adjusted for comorbidities and medications. Results: During 15.9 years of follow-up, 24,310 individuals (53.2%) died. The adjusted association between CRF and mortality risk was inverse and graded. For each 1-MET increase in CRF, the adjusted HR for mortality was 12% lower (HR, 0.88; 95% CI, 0.875 to 0.885; P<.001). When risk was assessed across CRF categories using the least-fit CRF category as the referent, the adjusted HRs and CIs were 0.76 (95% CI, 0.73 to 0.78), 0.63 (95% CI, 0.61 to 0.66), 0.49 (95% CI, 0.47 to 0.51), and 0.33 (95% CI, 0.30 to 0.35), for low-fit, moderate-fit, fit, and high-fit individuals, respectively. The pattern of the CRF mortality risk association was similar regardless of age, race, or sex. Conclusion: In this large multiethnic study, we found an independent, inverse, and graded association between CRF and mortality in CKD patients. These findings underscore the importance of increasing CRF in CKD patients to lower the risk of mortality.