Physical activity in patients with pre‑dialysis chronic kidney disease is associated with decreased renal function

Abstract

To the Editor Physical activity (PA) is associated with renal function in patients with pre-dialysis chronic kidney disease (CKD) [1, 2]. In these patients, higher PA levels have been noted to reduce the decline in kidney function [2, 3]. However, previous studies have used questionnaires to assess PA, and there are few objective surveys of PA using accelerometer–pedometers [2]. Thus, we aimed to objectively measure PA (via number of steps) and examine factors associated with decreased renal function in patients with pre-dialysis CKD. After baseline data were gathered from July 2014 to October 2015, this 2-year prospective cohort study was conducted from October 2015 to October 2017. The participants included 125 outpatients with pre-dialysis CKD stage G3–4 who could ambulate to our nephrology clinic [average age, 72.7 years; 78.4% men; mean estimated glomerular filtration rate (eGFR), 35.7 mL/min/1.73 m2]. We investigated patient characteristics including age, sex, body mass index (BMI), presence of diabetes, and biochemical parameters including eGFR, urine protein (UP), hemoglobin (Hb), serum albumin, and HbA1c at baseline. We used accelerometer–pedometers to assess the number of daily steps taken as a measure of PA at baseline [4]. To count daily steps, accelerometer–pedometers were worn for 1 week, and the mean value over that period was calculated. Patients were divided into two groups according to the median rate of change in renal function over the 2-year study period. Stepwise multiple regression analysis was conducted using factors showing a single correlation as the independent variables and the rate of change in renal function as the dependent variable. The characteristics of the patients are shown in Table 1. The rate of change in renal function at 2 years was -23.3% in the declining renal function group (n = 62) and − 0.9% in the maintaining renal function group (n = 63). The number of steps in the declining renal function group was significantly lower than that in the maintenance group: 4786.71 ± 2238.4 vs. 6608.0 ± 2938.1 steps/day, p < 0.01 (Fig. 1). The rate of change in renal function at 2 years correlated significantly with the number of steps (r = 0.42, p < 0.01), eGFR (r = 0.38, p < 0.01), UP (r = − 0.42, p < 0.01), and Hb (r = 0.30, p < 0.01). In the multiple regression analysis, the rate of change in renal function at 2 years significantly associated with number of steps, baseline eGFR, UP, and Hb in the patients with pre-dialysis CKD (R2 = 0.42, p < 0.01). A meta-analysis of exercise therapy for pre-dialysis CKD patients reported that exercise improves eGFR by an average of 2.62 mL/min/1.73 m2 [5]. Also, an observational study showed that CKD patients performing walking exercise had a significantly lower mortality rates and lower cumulative incidence of renal replacement therapy [3]. The present study revealed that number of steps, an objective measure of PA, is associated with maintaining renal function in predialysis CKD patients. Therefore, it is suggested that encouraging these patients to increase the number of steps taken * Koji Hiraki [email protected]