Neutrophil‐to‐Albumin Ratio Mediates the Association Between Life's Crucial 9 and Sarcopenia: A Cross‐Sectional Study

Background Emerging evidence links cardiovascular health, inflammation, and sarcopenia (SP), but the mediating mechanisms remain unclear. Life's Crucial 9 (LC9), a novel metric integrating mental health with cardiovascular risk factors, and neutrophil‐to‐albumin ratio (NPAR), a cost‐effective inflammatory biomarker, may jointly influence SP risk. This investigation seeks to examine the connection between LC9 and sarcopenia, assessing whether NPAR acts as a mediator in this relationship. Methods Multivariable logistic regression, smooth curve fitting, subgroup analysis, and other methods were employed to investigate the relationship between LC9 and the incidence of SP. Additionally, mediation analysis was conducted to examine the potential relationship between NPAR levels, LC9, and SP. Results This analysis involved 7,761 participants, of whom 648 reported experiencing SP events. After adjusting for all covariates using multivariable logistic regression, a 10‐point increase in LC9 was associated with a 37% reduction in the prevalence of sarcopenia (OR = 0.63, 95% CI: 0.59, 0.67). Additionally, sarcopenia increased by 1.17‐fold for each unit increase in NPAR (OR = 1.17, 95% CI: 1.11, 1.24). Conversely, the NPAR level and the highest quantile of SP prevalence increased by 2.26 times, respectively ( p < 0.001). Smooth curve fitting indicated a non‐linear relationship between LC9 and SP risk ( p for overall < 0.001, p for non‐linearity = 0.001). Subsequent threshold analysis identified a turning point at an LC9 score of 73.33; the risk of SP decreased gradually before this point, whereas a more pronounced and accelerated decline was observed once the score exceeded 73.33. Conclusion LC9 inversely correlates with SP, partially mediated by NPAR‐driven inflammation, suggesting anti‐inflammatory interventions may mitigate SP risk.