Appendicular Skeletal Muscle Mass and Insulin Resistance in an Elderly Korean Population: The Korean Social Life, Health and Aging Project-Health Examination Cohort

BACKGROUND: Increasing evidence supports an association between age-related loss of muscle mass and insulin resistance. However, the association has not been fully investigated in the general population. Thus, we investigated the association between appendicular skeletal muscle mass (ASM) and insulin resistance in an elderly Korean population. METHODS: This cross-sectional study included 158 men (mean age, 71.8) and 241 women (mean age, 70.6) from the Korean Social Life, Health and Aging Project, which started in 2011. In this study, ASM was measured by bioelectrical impedance analysis and was analyzed in three forms: ASM (kg), ASM/height(2) (kg/m(2)), and ASM/weight (%). The homeostasis model assessment of insulin resistance (HOMA-IR) was used as a measure of insulin resistance. The relationships between the ASM values and the HOMA-IR were investigated by multiple linear regression models. RESULTS: The HOMA-IR was positively associated with ASM (β=0.43, P<0.0001) and ASM/height(2) (β=0.36, P<0.0001) when adjusted for sex and age. However, after additional adjustment for body weight, HOMA-IR was inversely associated with ASM (β=-0.43, P<0.001) and ASM/height(2) (β=-0.30, P=0.001). Adjustment for other potential confounders did not change these associations. Conversely, HOMA-IR was consistently and inversely associated with ASM/weight before and after adjustment for other potential confounders. CONCLUSION: Our results support the idea that lower skeletal muscle mass is independently associated with insulin resistance in older adults. When evaluating sarcopenia or muscle-related conditions in older adults, their whole body sizes also need to be considered.