Muscle quality index is associated with advanced stages in patients with cardiovascular-kidney-metabolic syndrome: A cross-sectional study

Cardiovascular-kidney-metabolic (CKM) syndrome represents a complex systemic condition involving interconnected dysfunctions across metabolic, renal, and cardiovascular systems, presenting significant prevalence rates and imposing considerable clinical and economic challenges. Muscle mass and handgrip strength are recognized as independent prognostic indicators in cardiovascular, kidney, and metabolic diseases. The muscle quality index (MQI), integrating measures of muscle strength and mass, has demonstrated relevance for various health outcomes, but its association with advanced CKM syndrome remains unclear. This investigation employed a cross-sectional design utilizing National Health and Nutrition Examination Survey data from 2011 to 2014. The MQI was calculated as the ratio of handgrip strength to appendicular skeletal muscle mass. Advanced CKM syndrome was defined as stages 3 to 4 according to American Heart Association criteria. We employed multivariable logistic regression, restricted cubic spline analysis, and stratified analyses to examine the association between MQI and advanced CKM syndrome. Among 2012 participants, 4.7% had advanced CKM syndrome. Elevated MQI was associated with a reduced prevalence of advanced CKM syndrome (odds ratio = 0.54 per unit increase; 95% confidence interval = 0.29–0.99), with a threshold effect observed at MQI = 2.66, indicating stronger protection below this level. Notably, significant effect modifications by sex ( P -interaction = .0083) and income ( P -interaction < .0001) were observed: the inverse association was evident only in males and the highest-income individuals. Muscle quality exhibits a threshold-dependent effect against advanced CKM syndrome, with enhanced benefits in males and high-income populations. This suggests that maintaining muscle quality may be an important clinical consideration. Prospective longitudinal studies are warranted to clarify this association.