Sex-stratified non-linear associations between serum creatine phosphokinase and MASLD in U.S. adults: a cross-sectional analysis of NHANES 2017-March 2020

This is the authors' abstract. We don't add key points for this paper.

We examined whether the association between serum creatine phosphokinase (CPK) and metabolic dysfunction-associated steatotic liver disease (MASLD) is non-linear and sex-stratified in U.S. adults. This cross-sectional study included 5,219 participants from NHANES 2017–March 2020. MASLD was defined by vibration-controlled transient elastography (CAP ≥248 dB/m). Survey-weighted multivariable logistic regression and restricted cubic spline (RCS) models were performed. No significant linear association between CPK and MASLD was observed in either sex. In spline analyses, males showed a non-linear pattern with a descriptive U-shaped association, whereas the association in females was flatter and not statistically significant. Although non-linear modelling improved relative model fit, it did not meaningfully improve discrimination or calibration. These findings suggest an exploratory, sex-stratified, non-linear pattern that warrants confirmation in prospective cohorts with repeated CPK measurements and direct muscle phenotyping.