Triglyceride-related metabolic indices and low relative muscle mass: a cross-sectional analysis of SMILE and NHANES.

BACKGROUND

Lipid dysregulation may be associated with skeletal muscle impairment, but the relationships of routine triglyceride (TG)-based metabolic indices with low relative muscle mass remain unclear. We examined cross-sectional associations of serum TG and TG-based indices with ALM/BMI-defined low relative muscle mass, with exploratory analyses of low relative grip strength (Grip/BMI) and body-size coupling.

METHODS

Cross-sectional analyses included 1,084 adults from the SMILE study (2020-2025) and 5,034 adults from NHANES 2011-2018. Low relative muscle mass was operationally defined using the FNIH ALM/BMI thresholds and was not considered equivalent to clinically diagnosed sarcopenia. Multivariable logistic regression and survey-weighted logistic regression were used in SMILE and NHANES, respectively. Dose-response relationships were assessed using restricted cubic splines, and residual-based sensitivity analyses were used to examine body-size coupling.

RESULTS

Higher TG quartiles were associated with greater odds of low relative muscle mass. Fully adjusted ORs for the highest versus lowest TG quartile were 2.57 (95% CI, 1.44-4.59) in SMILE and 2.17 (95% CI, 1.33-3.53) in NHANES, with significant trends in both populations. Composite indices, especially TyG-WHtR, TyG-BMI, and METS-IR, showed larger associations. Grip/BMI findings were exploratory and more heterogeneous.

CONCLUSIONS

Higher TG and several TG-related composite indices were associated with ALM/BMI-defined low relative muscle mass in two complementary populations.