Metabolic age as a marker of cardiometabolic risk: Relationships with metabolic syndrome, hypertriglyceridemic waist, and hypertensive waist phenotypes in a large occupational cohort

BACKGROUND: Metabolic age (MA) has been proposed as an integrative, clinically intuitive indicator of physiological aging that may capture clustered cardiometabolic risk better than single traits. OBJECTIVE: We examined the association and discriminative performance of MA with metabolic syndrome (MetS) defined by NCEP ATP III, IDF, and Joint Interim Statement (JIS) criteria, and with the hypertriglyceridemic waist (HTGW) and hypertensive waist (HTAW) phenotypes, in a large occupational cohort. METHODS: Cross-sectional analytic study of Spanish workers attending routine occupational health examinations (January-June 2022). A total of 8590 employees (4104 men; 4486 women), aged 18-69 years, with standardized anthropometry, blood pressure, and fasting laboratory testing were included. MA was obtained via multifrequency bioelectrical impedance analysis; high MA was defined as MA ≥chronological age. Negative MA values (metabolic age lower than chronological age) indicate a metabolically younger or healthier profile, while positive values reflect accelerated metabolic aging and higher cardiometabolic risk. Five multivariable logistic models estimated adjusted odds ratios (ORs, 95% CI) for high MA across the five phenotypes; covariates included sex, age group, social class, smoking, physical activity, and Mediterranean diet adherence. Sex-stratified ROC analyses assessed discrimination (AUC); optimal thresholds were derived using Youden's index. RESULTS: High MA showed strong, independent associations with all phenotypes: MetS NCEP ATP III, OR 8.01 (95% CI 6.79-9.24); MetS IDF, OR 10.96 (9.23-12.80); MetS JIS, OR 7.94 (6.78-9.10); HTGW, OR 7.44 (6.10-8.79); HTAW, OR 13.97 (11.82-16.13). Behavioral and socioeconomic gradients were coherent across models (e.g., physical inactivity OR range 3.99-4.60; low Mediterranean diet adherence 2.38-2.61; smoking 1.17-1.23; lower social class III 2.27-2.42; men vs women 1.07-1.18). Sex-specific ROC analyses indicated good discrimination: AUCs (women/men) were 0.836/0.825 (NCEP ATP III), 0.835/0.833 (IDF), 0.819/0.807 (JIS), 0.813/0.849 (HTGW), and 0.827/0.865 (HTAW). Optimal MA cut-offs (difference MA-chronological age) ranged from -2 to +2 years across phenotypes and sex, yielding balanced sensitivity (∼75-82%) and specificity (∼75-77%). CONCLUSIONS: In a large occupational cohort, MA - derived from bioimpedance - was strongly and consistently associated with MetS (across three definitions) and with HTGW and HTAW, and it discriminated these phenotypes with AUCs ∼0.81-0.87. MA appears to be a feasible, low-burden metric that complements waist-based screening to prioritize preventive actions in workplace health programs. Longitudinal and interventional studies are warranted to confirm temporal relationships, refine MA thresholds by sex and age, and quantify incremental prognostic value beyond established risk indices.