Establishing The Relationship of Muscle Strength and Muscle Mass with 5-Year Clinical Outcomes in Kidney Transplantation (MO066)

Introduction and Aims: Sarcopenia, defined as loss of both skeletal muscle strength and mass, is associated with increased morbidity and mortality in ageing and chronic kidney disease populations. Recently, reduced muscle strength has been implicated as a more powerful prognostic index than muscle mass. In addition, changes in muscle strength may be discordant with those of muscle mass. Data on these muscular indexes are however lacking in kidney transplantation. The objectives of this study were to establish the prevalence of a) reduced muscle strength, b) reduced muscle mass, and c) a combination of both (sarcopenia), among kidney transplant recipients (KTRs), and assess their impact on 5-year graft survival, morbidity, and mortality.

Methods: This single-centre cross-sectional study enrolled 128 clinically stable KTRs (mean age=49±15 years; 56% male; and median time post-transplantation=5 years). Muscle strength was determined by handgrip strength (HGS) using hand dynamometer. Muscle mass was measured as lean tissue index (LTI) using bio-electrical impedance analysis. Reduced HGS, reduced LTI, and a combination of both (sarcopenia) were defined as ≤10th percentile of age- and gender-adjusted normative data for corresponding indexes. Follow-up data on 5-year graft survival, hospitalisation, and all-cause mortality were collected. Potential demographic, anthropometric, nutritional, and clinical predictors of graft survival, morbidity and mortality were assessed. Cox regression and Kaplan-Meier analyses were performed.

Results: Prevalence of reduced muscle strength, reduced muscle mass, and sarcopenia were 41%, 37%, and 21% respectively. Five-year death-censored and non-death censored graft failure rates were 9% and 15%. Five-year hospitalisation and mortality rates were 37% and 7%. Reduced HGS (adjusted hazard ratio [aHR]=4.99, p<0.05) and sarcopenia (aHR=4.30, p<0.05) were associated with increased mortality in multivariate Cox regression model. Additionally, reduced HGS (aHR=4.31, p<0.001) and sarcopenia (aHR=3.10, p<0.01) were associated with increased hospitalisation. Reduced HGS, reduced LTI, and sarcopenia did not predict 5-year graft failure (death-censored and non-death censored). No significant associations were found between reduced LTI and hospitalisation (p=0.10) as well as mortality (p=0.82). Kaplan-Meier analysis showed that HGS≤10th percentile led to higher hospitalisation (p<0.001, Figure 1) and mortality (p<0.05, Figure 2) rates. Sarcopenia depicted higher hospitalisation (p<0.001) and trended towards higher mortality (p=0.07) rates.

Conclusions: Reduced muscle strength, reduced muscle mass, and sarcopenia are common among KTRs. Reduced HGS and sarcopenia confer poor prognostic outlooks with their impact on mortality driven mainly by reduced muscle strength. Decreased muscle mass per se did not demonstrate prognostic value in this study. Future research should focus on strength-training based exercise, thereby improving morbidity and mortality in kidney transplantation.