Exercise capacity as a predictor of survival among ambulatory patients with end-stage renal disease

Background. Exercise capacity is reduced in end-stage renal disease (ESRD). Exercise requires the integrated function of multiple vital organs, and low exercise capacity is an independent predictor of mortality in a number of clinical populations. We analyzed the value of exercise capacity, characterized as peak oxygen uptake (VO2), for predicting survival in a cohort of 175 hemodialysis patients over a median follow-up of 39 months. Methods. Survival status was determined for 175 ESRD patients who had participated in previous studies for which peak VO2 and other clinical data had been determined. Chi-square and Kaplan-Meier survival analyses were performed, and a minimal model of factors related to mortality was developed by Cox multiple regression. Results. There were 23 deaths during the follow-up period. Peak VO2 (>17.5 mL/min/kg) was a powerful predictor of survival (P = 0.009 by Kaplan-Meier). Age (<65 years), dialysis vintage (<39 months), pulse pressure (<54 mm Hg), and absence of diagnoses of diabetes or heart failure were also associated with better survival on univariate analyses. On multivariate analysis peak VO2 contributed significantly to the minimal explanatory model relating clinical variables to mortality (overall chi(2) = 25.5, P = 0.00001). Conclusion. Among these ambulatory ESRD patients, peak VO2 was a stronger predictor of survival than many traditional prognostic variables, some of which are subject to ceiling effects. Exercise capacity may thus provide incremental prognostic information concerning healthier ESRD patients. Because peak VO2 may be modified by exercise training, the potential of exercise as an intervention to improve survival is suggested.