Appendicular skeletal mass/Trunk lean mass as a New Diagnostic Marker of Sarcopenia in population study

Abstract

Background: Muscle mass decreases with age, leading to sarcopenia in elderly people. Sarcopenia is believed to be associated with metabolic, physiological, and functional impairmen`ts and disability. However, there is no gold standard for its diagnosis. In this study, we compared 2 sarcopenia definitions [i.e., appendicular skeletal mass (ASM)/(height (ht))2 vs. ASM/trunk lean mass (TLM)] regarding their relationship with metabolic syndrome, insulin resistance, and health-related quality of life. Subjects and Methods: The data from a population-based survey, namely, the The Korea National Health and Nutrition Examination Survey (KNHANES) IV (3,290 subjects), were analyzed. To define sarcopenia, we used ASM/(ht)2 and ASM/TLM at a value more than 2 SD below the mean of a young reference group. Metabolic syndrome was defined according to the International Diabetes Federation definition, and insulin resistance was measured using the homeostasis model assessment of insulin resistance (HOMA-IR). To evaluate quality of life, we used the EuroQoL (EQ)-5D. Results: The prevalence of sarcopenia in men and women as determined by ASM/(ht)2 was 31.2% and 8.8%, respectively, and by ASM/TLM was 32.6% and 28.5%, respectively. When adjusted by age, exercise, smoking, alcohol, and fat mass index, sarcopenia as determined by ASM/TLM values increased the risk of metabolic syndrome 1.132 times (95% CI = 1.123–1.141) in men and 2.383 times (95% CI =2.306–2.463) in women. HOMA-IR was positively correlated with ASM/(ht)2 (men: B =0.0.094, p = 0.029; women: B = 0.265, p < 0.001) and negatively correlated with ASM/TLM (men: B = −2.308, p < 0.001; women: B = −1.003, p < 0.001). ASM/(ht)2 was only correlated with EQ-5D in men, whereas ASM/TLM was correlated with EQ-5D in both genders. In multiple regression with ASM/(ht)2, ASM/TLM ratio, age, and fat mass index, ASM/Ht2 (R2 = 0.120, B = 0.010, p < 0.001) in men and ASM/TLM (R2 =0.210, B = 0.099, p = 0.022) in women were correlated with the EQ-5D index. Conclusion: We examined the prevalence of sarcopenia in Korean men and women from the data from a national representative study (the KNHANES IV). ASM/TLM was more valid than ASM/(ht2) in observing metabolic changes associated with decreasing muscle mass. We also found that ASM/TLM was significantly correlated with sarcopenia and health-related quality of life.