Association between Cardiometabolic Index (CMI) with muscle mass and strength in US adults: A cross-sectional study

Cardiometabolic Index (CMI) is a comprehensive indicator of lipid metabolism and visceral fat distribution, but its relationship with skeletal muscle mass and muscle strength remains unclear. We therefore explored the relationship between CMI and muscle health, providing new insights into the overall assessment of metabolic health. This cross-sectional study analyzed data from the National Health and Nutrition Examination Survey 2011-2014 cycles, including 2719 adults aged ≥ 18 years. During the study, participants' Appendicular Skeletal Muscle Mass Index (ASMI) was determined using dual-energy X-ray absorptiometry, while their grip strength was measured by applying a dynamometer. CMI was calculated as triglycerides divided by high-density lipoprotein cholesterol, multiplied by waist-to-height ratio. Models were adjusted for age, sex, race/ethnicity, education, body mass index (BMI), lifestyle factors, and comorbidities. The correlation between CMI and skeletal muscle mass and grip strength was explored through weighted generalized linear regression modeling. Restricted cubic spline models were used to explore nonlinear associations and threshold effects. Further subgroup analyses were performed to clarify the moderating role of factors such as gender, ethnicity, and BMI in these relationships. CMI showed a significant positive correlation with ASMI (fully adjusted model: β = 1.01, 95% confidence intervals: 0.86-1.17, P < .0001) and showed a nonlinear relationship: at lower levels of CMI (<0.6), the strongest effect of CMI on ASMI was observed (β = 5.09); at higher levels (>0.6), this effect was significantly weaker (β = 1.46). Preliminary models of CMI and grip strength showed a positive correlation (Model 1: β = 2.74, 95% confidence intervals: 2.02-3.46, P < .0001), but this correlation weakened and became nonsignificant in the fully adjusted model. Subgroup analyses indicated that gender, race, and body mass index significantly moderated the relationship between CMI and ASMI, with females, non-Hispanic blacks, and high BMI being more strongly associated with ASMI. CMI is significantly positively correlated with skeletal muscle mass, and this association exhibits nonlinear and threshold effects. The relationship between CMI and muscle strength is more complex and may be influenced by other confounding factors.