Physical inactivity and protein energy wasting play independent roles in muscle weakness in maintenance haemodialysis patients

Background Muscle weakness is associated with increased mortality risk in chronic haemodialysis (CHD) patients. Protein energy wasting (PEW) and low physical activity could impair muscle quality and contribute to muscle weakness beyond muscle wasting in these patients. Aim of this study was to assess clinical and biological parameters involved in the reduction of muscle strength of CHD patients. Methods One hundred and twenty-three CHD patients (80 males, 43 females; 68,8 [57.9-78.8] y.o.) were included in this study. Maximal voluntary force (MVF) of quadriceps was assessed using a belt-stabilized hand-held dynamometer. Muscle quality was evaluated by muscle specific torque, defined as the strength per unit of muscle mass. Muscle mass was estimated using lean tissue index (LTI), skeletal muscle mass (SMM) assessed by bioelectrical impedance analysis and creatinine index (CI). Voorrips questionnaire was used to estimate physical activity. Criteria for the diagnosis of PEW were serum albumin, body mass index < 23 kg/m(2), creatinine index < 18.2 mg/kg/d and low dietary protein intake estimated by nPCR < 0.80g/kg/d. Results MVF was 76.1 [58.2-111.7] N.m. and was associated with CI (beta = 5.3 [2.2-8.4], p = 0.001), LTI (beta = 2.8 [0.6-5.1], p = 0.013), Voorrips score (beta = 17.4 [2.9-31.9], p = 0.02) and serum albumin (beta = 1.9 [0.5-3.2], p = 0.006). Only serum albumin (beta = 0.09 [0.03-0.15], p = 0.003), Voorrips score (beta = 0.8 [0.2-1.5], p = 0.005) and CI (beta = 0.2 [0.1-0.3], p<0.001) remained associated with muscle specific torque. Thirty patients have dynapenia defined as impaired MVF with maintained SMM and were younger with high hs-CRP (p = 0.001), PEW criteria (p<0.001) and low Voorrips score (p = 0.001), and reduced dialysis vintage (p<0.046). Conclusions Beyond atrophy, physical inactivity and PEW conspire to impair muscle strength and specific torque in CHD patients and could be related to muscle quality.