Effects of different definitions of low muscle mass on its association with metabolic syndrome in older adults: A Korean nationwide study

Aim We aimed to investigate the association between low muscle mass (LMM) and metabolic syndrome (MetS) according to the definition of LMM. Methods This study used data from the Korean National Health and Nutrition Examination Survey conducted from 2008 to 2011. We used appendicular skeletal muscle adjusted for height (ASM/Ht2) and weight (ASM/Wt) as definitions of LMM. Class I and Class II LMM were defined as ASM/Ht2 or ASM/Wt from 1 to 2 standard deviations (SDs) or 2 SDs below the mean for young adults, respectively. Results A total of 6370 participants were included in analysis: 58.5% were women. The mean age of participants in this study sample was 72.3 ± 4.8 years. In the fully adjusted model, ASM/Ht2 was inversely related to MetS prevalence (adjusted odds ratio [aOR] 0.770, 95% confidence interval [CI] 0.600–0.988 for class I, aOR 0.473, 95% CI, 0.327–0.684 for class II). In contrast, MetS prevalence increased in class I (aOR 1.902, 95% CI 1.510–2.396) and class II LMM (aOR 2.831, 95% CI 2.194–3.655) using ASM/Wt. ASM/Ht2 was proportional to the waist circumference and the number of metabolic features, whereas ASM/Wt was inversely proportional in both sexes. Stratified analysis showed that the association was robust regardless of the cardiovascular risk factors. Conclusion In Korean older adults, ASM/Wt is positively associated with MetS prevalence, whereas ASM/Ht2 is inversely associated, regardless of the cardiovascular risk factors. Waist circumference and the number of metabolic features were directly proportional to ASM/Ht2, but inversely proportional to ASM/Wt. Geriatr Gerontol Int 2021; 21: 1003–1009.