Prevalence of sarcopenia and relationships between muscle and bone in Indian men and women

Background: both ethnicity and age are important determinants of musculoskeletal health. We aimed to determine the prevalence of sarcopenia, assess the suitability of current diagnostic guidelines, and explore muscle-bone relationships in adults from India. Methods: 1009 young (20-35years) and 1755 older (>40years) men and women from existing studies were collated and pooled for the analysis. Dual-energy x-ray absorptiometry measured areal bone mineral density (aBMD) at the hip and spine, and fat and lean mass; hand dynamometer measured hand grip strength (HGS). Indian-specific cut-points for appendicular lean mass (ALM), ALM index (ALMI) and HGS were calculated from young Indian (-2SD mean) populations. Sarcopenia was defined using cut-points from The Foundations for the National Institutes of Health (FNIH), revised European Working Group on Sarcopenia in Older People (EWGSOP2), Asian Working Group for Sarcopenia (AWGS), and Indian-specific cut-points. Low lean mass cut-points were then compared for their predictive ability in identifying low HGS. The relationship between muscle variables (ALM, ALMI, HGS) and aBMD were explored, and sex differences were tested. Results: Indian-specific cut-points (men-HGS:22.93kg, ALM:15.41kg, ALMI:6.03kg/m2; women-HGS:10.76kg, ALM:9.95kg, ALMI:4.64kg/m2) were lower than existing definitions. The Indian-specific definition had the lowest, while EWGSOP2 ALMI had the highest predictive ability in detecting low HGS (men:AUC=0.686, women:AUC=0.641). There were sex differences in associations between aBMD and all muscle variables, with greater positive associations in women than in men. Conclusion: the use of appropriate cut-points for diagnosing low lean mass and physical function are necessary in ethnic populations for accurate sarcopenia assessment. Muscle-bone relationships are more tightly coupled during ageing in Indian women than men