The Associations of Muscle Strength, Muscle Mass, and Adiposity With Clinical Outcomes and Quality of Life in Prevalent Kidney Transplant Recipients

Abstract

Objective: Sarcopenia, defined as loss of both muscle strength and mass, is associated with inferior clinical outcomes and quality of life (QoL) in chronic kidney disease, but its effects are unknown in kidney transplantation. Obesity confers increased mortality risk and compromises QoL in kidney transplant recipients (KTRs), but the impacts of sarcopenic obesity remain unexplored. This study aimed to evaluate the associations of muscle strength and mass, sarcopenia, and sarcopenic obesity with clinical outcomes and QoL in KTRs.

Methods: This prospective longitudinal study enrolled 128 KTRs ≥1-year posttransplantation. Low muscle strength (by handgrip strength) and mass (by bioimpedance analysis), and a combination of both (sarcopenia) were defined as < reference cutoffs for corresponding indices. Sarcopenic obesity was defined as sarcopenia combined with fulfillment of ≥2 out of 3 criteria from (1) body mass index ≥30 kg/m², (2) bioimpedance analysis-derived fat mass > reference cutoffs, and (3) waist circumference > World Health Organization cutoffs. Prospective follow-up data on mortality and hospitalization were collected. QoL was evaluated using Medical Outcomes Study Short Form-36 questionnaire.

Results: Median follow-up duration was 64 (60-72) months. Low muscle strength was independently associated with the composite endpoint of mortality and hospitalization (hazard ratio = 2.45; P = .006), and QoL (physical-related: β = -12.2; P = .04; mental-related: β = -9.9; P = .04). Low muscle mass (β = -8.8; P = .04) and sarcopenia (β = -14.7; P = .03) were associated with physical-related QoL only. No independent associations were found between muscle mass, sarcopenia, and sarcopenic obesity with the composite outcome of mortality and hospitalization.

Conclusion: Low muscle strength is common among KTRs, conferring poor prognosis in the medium term. Future research on strength training may prove valuable in improving kidney transplantation outcomes.