Secondary sarcopenia in spinal cord injured subjects

Abstract

The European Working Group on Sarcopenia in Older People (EWGSOP) categorized sarcopenia in primary-age related and secondary sarcopenia. Whole body Dual-energy X-ray Absorptiometry (DXA) measurement remains the gold standard for muscle mass measurements. Sarcopenia is defined by measuring muscle mass (ratio of appendicular skeletal mass (ASM)/height 2 (kg/m 2 ), (skeletal muscle index, SMI) and muscle strength. An alternative for muscle strength (in Newton, N) is muscle cross- sectional area (CSA) in cm 2 (a surrogate for muscle effectiveness or loading-force). The present study investigated if a similar approach to define secondary sarcopenia in spinal cord injured subjects. The study included 31 paraplegics with complete paraplegia compared with 50 controls. All were examined by whole body DXA (Norland XR 36, USA) regarding muscle mass (relative appendicular skeletal mass (RASM), in Kg) and peripheral quantitative computed tomography (pQCT XCT-3000, Stratec, Germany) in 66% of tibia's length (muscle CSA, mm 2 ). Sarcopenia in the spinal cord injured subjects was defined as SMI, as well as relative ASM, RASM) by the residual method, respectively. Paraplegics had significantly lower values in muscle area (CSA) and RASM ( P < 0.001) compared to controls. In the adjusted analysis according to age, height and relative fat mass, paraplegia was associated with lower values of RASM (beta ± se; −2.74 ± 0.28, P < 0.001). In SCI paraplegics muscle CSA can be measured. Muscle mass can be measured also. This study suggests that we may categorize paraplegics with the current functional definition of EWGSOP for sarcopenia for research purposes. The sensitivity and specificity of this measurement remains unclear.