Can Functional Motor Capacity Influence Mortality in Advanced Chronic Kidney Disease Patients?

Alterations in the body's nutritional status or composition may be observed as the kidney disease advances, which could influence the kidney's functional capacity and, consequently, could increase the risk of mortality. The aim of the study is to determine the influence of functional capacity on mortality assessed by different functional tests in patients with advanced chronic kidney disease (ACKD). A prospective observational study was designed, which included 225 patients followed for 8 years in a CKD clinic. The study assessed functional capacity by using a range of tests, which included the Short Physical Performance Battery, the 6 minutes walking gait test, the timed up and go, and the four versions of the sit-to-stand test. Additionally, body composition and nutritional conditions were considered, taking into consideration various biochemical indicators such as albumin, prealbumin, c-reactive protein (CRP), lymphocytes, and transferrin, muscle strength, comorbidity, and frailty. The relationship between functionality and all-cause mortality was investigated using a Cox proportional hazard model. A total of fifty patients died during the duration of the study. Patients who performed worse on the function and muscle strength tests showed a worse body composition and nutritional status, and exhibited a reduced life expectancy. Inflammation (CRP) was associated with an increased risk of mortality (model 1: hazard ratio (HR) = 1.246; 95% confidence interval (95% CI = 1.014-1.531; model 2: HR = 1.333; 95% CI = 1.104-1.610). Good functional capacity as determined by the SPPB test decreased the risk of mortality (model 1: HR = 0.764; 95% CI = 0.683-0.855; model 2 HR = 0.778; 95% CI = 0.695-0.872). Cut-off points of maximum sensitivity and specificity for mortality were obtained with different tests. The study demonstrated that functional capacity influences mortality in patients with ACKD, being higher in those patients with impaired functionality regardless of the test used, although the SPPB allows a larger number of patients to be assessed. Therefore, it is essential to incorporate the assessment of functionality into the comprehensive care of patients with CKD.