The psoas muscle index distribution and influence of outcomes in an Asian adult trauma population: an alternative indicator for sarcopenia of acute diseases

Background: Sarcopenia has been shown to be an independent negative predictor in various diseases. The measurement of pre-defined criteria of skeletal muscle in patients with acute disease is usually unavailable. Therefore, we evaluate the psoas muscle area based on computed tomography (CT) imaging as an alternative for sarcopenia in an Asian trauma population. Methods: 939 trauma patients were enrolled and had CT imaging performed primarily for trauma indications. The cross-sectional area of psoas muscle at the base of the fourth lumbar vertebral was measured on these CTs. Psoas muscle index (PMI) was calculated and analyzed to determine sex-specific cut-off values to define the “extremely low psoas muscle index” (ELPMI) group. Results: Psoas muscle index was significantly higher in males (1065.09 ± 230.51 mm²/m² in males vs 719.57 ± 147.39 mm²/m² in females, p < 0.001) and decreased gradually with aging (p < 0.001). PMI of the subset of patients aged 18–40 (n = 462) weas analyzed to determine sex-specific cut-off values for ELPMI. PMI cut-off values for ELPMI (2 SD below mean) were 675 mm²/m² for males and 490 mm²/m² for females. The entire trauma cohort was further analyzed, and ELPMI was identified as an independent risk factor for a longer length of intensive unit stay (β coefficient = 3.881, p = 0.011). Conclusion: Data from young trauma adults were used to establish cut-off values for ELPMI, which is a longer ICU stay predictor. These cut-off values for ELPMI may apply to other acute disease entities.