Defining Sarcopenia in the Indian Population—a Step Forward

Abstract

Decline in muscle mass and function has been associated with frailty syndrome and other chronic medical conditions. Poor outcomes following treatment have been reported in various gastrointestinal malignancies in sarcopenic patients. The Asian Working Group of Sarcopenia has suggested 2 standard deviation below the mean muscle mass of a young reference group, as the cut-off point for defining this entity. However, values vary according to ethnicities, and no study has previously assessed muscle indices in the Indian population. The study aims to access muscle area and density as markers of sarcopenia and to define sex specific cut off points for the Indian population. This is a prospective study conducted at the Medanta Hospital from May 2016 to March 2018. Prospective organ donors, in age group of 18 to 65 years, were enrolled in this study. Computed tomography scan of the abdomen (used for preoperative evaluation) was used to evaluate psoas muscle area and density at the level of transverse processes of the third and fourth lumbar vertebrae. Plain scan images with 3 mm cuts were used for calculations. Psoas area was normalized for height, and density was normalized for weight. Mean of psoas area (acquired at L3 and L4 levels) was normalized for height, and values less than 2 standard deviation (SD) below the mean were calculated. Similar calculations were done for psoas density. Values using 1.64SD below the mean, 5th percentile and 10th percentile were calculated as well. There were 457 healthy donors who were enrolled in the study, but 26 were excluded from the analysis as they belonged to non-Indian ethnicities. Sex-specific values were calculated. Values at 2SD below the mean, 1.64SD below the mean, 5th percentile and 10th percentile for the male population were 173.8 mm²/m², 210.7 mm²/m², 220.7 mm²/m² and 239.05 mm²/m², respectively, for psoas area. Similar values for psoas density were 0.48, 0.53, 0.56 and 0.575 Hounsfield units/kg, respectively. For the female cohort, values at 2SD below the mean, 1.64SD below the mean, 5th percentile and 10th percentile, for psoas density, were 101.2 mm²/m², 128.7 mm²/m², 149.5 mm²/m² and 173.80 mm²/m², respectively. Values for psoas density were 0.26, 0.36, 0.53 and 0.59 Hounsfield units/kg, respectively. 5th percentile values and values at 1.64SD below the mean were found to be more concordant, and we have decided to take 5th percentile values as the cut-off point to define sarcopenia for further studies. We defined sarcopenia at 5th percentile, with sex-specific cut-off points for psoas area and density. Defining this parameter is important as there has been a substantial increase in the elderly population. Studies have shown poor outcomes in patients with sarcopenia, when managing them for chronic illnesses and malignancy.