Relationship between Muscle Mass, Strength, and Physical Performance in Patients on Maintenance Hemodialysis

Background: A relationship between muscle mass, muscle strengh, and physical performance in hemodialysis (HD) patients could be not established by a unidirectional pathway. This study aimed to assess the causal association of the aforementioned three variables using a mediation analysis. Methods: We included 84 HD patients. The collected data included appendicular lean mass index (ALM/Ht2), handgrip strength (HGS), gait speed (GS), five-times sit-to-stand test, 30-s-sit-to-stand test (STS30), 6-min walk test (6MWT), timed up and go test, and short physical performance battery. Mediation analysis was done using Baron and Kenny’s regression approach to investigate the mediating effect. Results: The mean ALM/Ht2 and HGS were 6.6 ± 1.0 kg/m2 and 26.1 ± 7.4 kg, respectively. ALM/Ht2 or HGS showed a positive association with GS, STS30, or 6MWT, and the association between ALM/Ht2 and HGS was significant. After adjusting for HGS, the association between ALM/Ht2 and three physical performances did not remain significant; however, after adjusting for ALM/Ht2, the association between HGS and three physical performances remained significant. Conclusion: The present study demonstrated that physical performance tests were associated with both ALM/Ht2 and HGS, but the association between ALM/Ht2 and physical performance tests is completely mediated by HGS.