Psoas muscle index and psoas muscle density as predictors of mortality in patients undergoing hemodialysis

This study aimed to investigate the associations of computed tomography (CT)-measured psoas muscle index (PMI: psoas muscle area normalized by height) and psoas muscle density (PMD: average of bilateral psoas muscle CT values [Hounsfield unit (HU)]) with mortality in patients undergoing hemodialysis. We included 188 hemodialysis patients who underwent abdominal CT. PMI and PMD were measured at the third lumbar vertebral level. We found that PMI and PMD were independently associated with the geriatric nutritional risk index and log C-reactive protein, respectively. The optimal cut-off values of PMI and PMD for men and women were 3.39 cm(2)/m(2) and 41.6 HU, and 2.13 cm(2)/m(2) and 37.5 HU, respectively. During follow-up (median 3.5 years), 69 patients died. Lower PMI and lower PMD were independently associated with an increased risk of all-cause mortality [adjusted hazard ratio (aHR) 2.05, 95% confidence interval (CI) 1.14-3.68; aHR 3.67, 95% CI 2.04-6.60), respectively]. The aHR for lower PMI and lower PMD vs. higher PMI and higher PMD was 5.34 (95% CI 2.38-11.97). The addition of PMI and PMD to the risk model significantly improved C-index from 0.775 to 0.893 (p < 0.00001). The combination of PMI and PMD may improve mortality prediction in patients undergoing hemodialysis.