Association of cardiometabolic index with spondyloarthritis and its impact on health-related quality of life: Findings from NHANES 2009-2010

BACKGROUND: Cardiometabolic index (CMI) is a novel marker reflecting metabolic and cardiovascular health, but its role in spondyloarthritis (SpA) remains unclear. This study aimed to investigate the association between CMI and SpA and its potential impact on individual health. METHODS: A total of 340 participants were included after propensity score matching, stratified into SpA and non-SpA groups. Baseline characteristics were analyzed, followed by collinearity analysis. The importance of CMI in SpA was assessed using two machine learning methods. Restricted cubic splines (RCS) and logistic regression analyses were conducted to evaluate the association between CMI and SpA. Interaction and subgroup analyses further examined potential modifying effects. The association of CMI with health-related quality of life (HRQoL) indicators was analyzed using regression models. Finally, mediation analysis was performed. RESULTS: CMI was significantly higher in the SpA group (P < 0.001) and emerged as the most influential factor in SpA classification models. RCS analysis demonstrated a positive association between CMI and SpA. Multivariate regression revealed that higher CMI tertiles were associated with increased SpA risk (T3 vs. T1: OR = 3.368, P = 0.001). Hypertension significantly modified this relationship (P for interaction = 0.046). Additionally, higher CMI was linked to poorer self-rated health and increased physically unhealthy days (P < 0.05). Mediation analysis indicated that SpA mediated the relationship between CMI and health outcomes. CONCLUSIONS: CMI is associated with SpA and HRQoL indicators. SpA mediates the relationship between CMI and physical health, highlighting the importance of CMI in SpA risk assessment and patient management.