Application of current sarcopenia definitions in spinal cord injury

Abstract

Objective: Little is known about how appropriate the working definitions of sarcopenia are in subjects with spinal cord injury (SCI). This study aimed to evaluate the application of current sarcopenia definitions in SCI.

Methods: We compared 31 complete SCI men with 33 able-bodied age matched subjects. All were examined by whole body DXA (Norland XR 36, USA) regarding muscle and fat mass and by peripheral quantitative computed tomography (pQCT XCT-3000, Germany) in 66% of tibia's length (muscle cross sectional area, (CSA) in mm²). Low muscle mass was defined by skeletal muscle index, (SMI= appendicular lean mass (aLM)/height² in Kg/m²) and by the residual method: relative aLM, 20^th percentile of the distribution of residuals as the cutoff point, (RASM), respectively. CSA is a surrogate for force.

Results: We found lower values on RASM (p<0.001), and SMI (p<0.001) compared to controls in SCI and difference in the rate of sarcopenia according to sarcopenia definitions. CSA was significantly decreased in SCI (p<0.001) and correlation with duration of paralysis was weak.

Conclusion: Current functional definitions of sarcopenia classify different individuals as sarcopenic. Sarcopenia was more prevalent in SCI. The sensitivity and specificity of using these measurements in SCI remain unclear.

Figure 1

A comparison of the methods used to define relative lean mass (aLM/ht² and regression residuals method including fat mass) in both groups. Residuals (obtained from linear regression of appendicular lean mass (aLM) (kg) on height (meters) and fat mass (kg)) and the ratio (aLM/ht²) of aLM (kg) and height squared (m²). Horizontal and vertical lines indicate the 20th percentile of residuals and aLM/ht² distributions, respectively. Frequencies in each quadrant are indicated by n.

Figure 2

A comparison of the methods used to define relative lean mass (aLM/ht² and regression residuals method including fat mass) in both groups using cut off 7.26 as Baumgartner proposed[7]. Residuals (obtained from linear regression of appendicular lean mass (aLM) (kg) on height (meters) and fat mass (kg)) and the ratio (aLM/ht²) of aLM (kg) and height squared (m²). Horizontal and vertical lines indicate the 20th percentile of residuals and aLM/ht² distributions, respectively. Frequencies in each quadrant are indicated by n.

Figure 3

Prevalence of sarcopenia by method, RASM and residuals obtained from linear regression of RASM on height and total fat mass.

Figure 4

Prevalence of sarcopenia by method, SMI cut-off 7.26 and residuals obtained from linear regression of SMI on height and total fat mass.