Muscle Mass, Muscle Strength, and Health-Related Quality of Life in Kidney Transplant Recipients: Results of the TransplantLines Biobank and Cohort Study

Introduction: Muscles are crucial for daily activities, and kidney transplant recipients (KTRs) often have reduced muscle mass and strength. We aimed to investigate the potential relationship of muscle mass and strength with physical health-related quality of life (HRQoL) in KTRs.

Methods: Data from the TransplantLines Biobank and Cohort Studies were used. Muscle mass was assessed using appendicular skeletal muscle mass index (ASMI) and 24-hour urinary creatinine excretion rate index (CERI). Muscle strength was assessed by handgrip strength index (HGSI). HRQoL was measured using Short Form 36 physical component score (PCS).

Results: We included 751 KTRs (61% male; mean age, 56 ± 13 years, median of 3 years post-transplant). Ordinary least squares regression analyses demonstrated that lower ASMI, CERI, and HGSI were all nonlinearly associated with lower PCS, independent of potential confounders and each other. Below median values, ASMI, CERI, and HGSI were each associated with PCS; whereas above median values, associations were less pronounced. Compared to the 50th percentile, a decrease to the 10th percentile was associated with a change in PCS of −4.8% for ASMI (P = 0.011), of −5.1% for CERI (P = 0.008), and −13.2% for HGSI (P < 0.001), whereas an increase to the 90th percentile was associated with a change in PCS of only +0.7% for ASMI (P = 0.54), of +3.6% for CERI (P = 0.05), and −0.4% for HGSI (P = 0.73).

Conclusion: Low muscle mass and strength are potentially modifiable risk factors for impaired physical HRQoL in KTRs. The nonlinear associations suggest that KTRs with low muscle mass or strength may particularly benefit from (p)rehabilitation interventions to improve HRQoL.