Association between Skeletal Mass Indices and Metabolic Syndrome in Brazilian Adults

Introduction: Skeletal muscle is the primary site of glucose uptake and its reduction would increase insulin resistance, which is a determinant factor for diseases such as type 2 diabetes mellitus, hypertension, and metabolic syndrome. However, the role of low skeletal muscle mass as a risk factor for metabolic syndrome and its association with cardiometabolic risk is still uncertain. We aimed to investigate the association between muscle mass (determined by different skeletal mass indices) and metabolic syndrome in Brazilian adults. Methodology: We conducted a cross-sectional population-based study with 689 adults of both sexes aged between 20 and 59 years. Data were collected through questionnaires and assessment of body composition through dual-energy X-ray absorptiometry and anthropometric, clinical, and biochemical measurements. Results: Older individuals, obese and those with metabolic syndrome predominated in the highest tertile of skeletal mass index adjusted by height (SMIheight), whereas using skeletal mass index adjusted by weight (SMIweight) and skeletal mass index adjusted by body mass index (SMIBMI) these individuals were the majority in the lowest tertile of these indices. In men and women, the adjusted logistic regression model revealed that the highest tertile of SMIweight (odds ratio [OR]: 0.06; 95% confidence interval [CI]: 0.02−0.21 and OR: 0.27, 95% CI: 0.10−0.74) and SMIBMI (OR: 0.14, 95% CI: 0.05−0.37 and OR: 0.34, 95% CI: 0.12−0.94) were negatively associated with metabolic syndrome. On the other hand, the highest tertile of SMIheight was positively associated with metabolic syndrome in both sexes (OR: 4.17, 95% CI: 1.80−9.66 and OR: 6.15, 95% CI: 2.31−16.37, respectively in men and women). Conclusion: In adults, the muscle mass assessed from the skeletal mass index adjusted for body weight and body mass index is inversely associated with metabolic syndrome in both sexes.