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/Ht ) and weight (ASM/Wt) as definitions of LMM. Class I and Class II LMM were defined as ASM/Ht 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/Ht 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/Ht 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/Ht is inversely associated, regardless of the cardiovascular risk factors. Waist circumference and the number of metabolic features were directly proportional to ASM/Ht , but inversely proportional to ASM/Wt. Geriatr Gerontol Int 2021; 21: 1003-1009.