Cardiorespiratory Fitness And Mortality In Patients With Chronic Kidney Disease

PURPOSE: Chronic kidney disease (CKD) is associated with increased risk of mortality. A few studies have associated physical activity with mortality risk in patients with chronic kidney disease (CKD). However, limited studies have been conducted on the association between objectively assessed cardiorespiratory fitness (CRF) and mortality in CKD patients. METHODS: From a large cohort of US Veterans (n = 750,302) based on the DCVAMC (ETHOS study), we identified 47,299 men and women ages 30 to 95 years (mean age 65.0 ± 8.7 years), who completed an exercise treadmill test (ETT) within the Veterans Affairs hospitals across the United States. All were diagnosed with CKD at least six months post-ETT by ICD-9 and ICD-10 codes and verified by at least 2 consecutive estimated glomerular filtration rate values of less than 60 mL/min per 1.73 m2 at least 3 months apart. Age-and-sex-specific CRF categories (Quintiles) were established objectively based on peak metabolic equivalents (METs) achieved during the ETT. We computed hazard ratios (HRs) and 95% confidence intervals (CIs) with Cox regression analyses adjusted for co-morbidities and medications. RESULTS: During the follow-up (median of 12.7 years) and 596,978.0 person-years, 25,109 individuals (53.1%) died. The adjusted association between CRF and mortality risk was inverse and graded. For each 1-MET in CRF increase the adjusted HR for mortality was 12% (HR 0.88; 95% CI: 87-89; P < 0.001). When risk was assessed across CRF categories using the least fit CRF category as the referent, the adjusted HRs and CIs were 0.75 (0.73-0.77), 0.63 (0.61-0.65), 0.49 (0.47-0.51), and 0.33 (0.30-0.35), for Low-fit, Moderate, Fit and High-fit individuals, respectively. The pattern of the CRF-mortality risk association was similar regardless of race or gender. CONCLUSIONS: In this large multi-ethnic study, we found an independent, inverse, and graded association between CRF and mortality in CKD patients. These findings underscore the importance of advocating physical activity in CKD patients to increase CRF and lower the risk of mortality.