Lipid–metabolic risk stratification for carotid plaque in adults under 50 years undergoing health examinations: cross-sectional modeling and same-center longitudinal validation

Carotid plaque is an imaging marker of early subclinical atherosclerosis. Adults under 50 years of age undergoing health examinations often have low short-term absolute cardiovascular risk, yet adverse lipid–metabolic profiles may already be associated with early plaque formation. This study aimed to develop and evaluate a parsimonious lipid–metabolic risk stratification model for carotid plaque risk using routinely available health-examination variables. This retrospective single-center study constructed two related cohorts from a health management center. The cross-sectional modeling cohort included 30,557 adults under 50 years of age examined between 2018 and 2023, of whom 1277 had prevalent carotid plaque, and was used for model development and internal validation. The same-center longitudinal validation cohort included 1679 baseline plaque-free participants with classifiable longitudinal plaque trajectories from repeated examinations between January 2020 and December 2024; 105 developed the primary incident carotid plaque outcome. Thirteen routine health-examination variables were considered. Variable selection and model development were performed only in the training set. The final multivariable logistic regression model included age, male sex, low-density lipoprotein cholesterol, systolic blood pressure, high-density lipoprotein cholesterol, and fasting glucose. Performance was assessed using AUROC and PR-AUC. Low-, intermediate-, and high-risk strata were defined using tertiles of predicted probability in the training set. In the internal validation set, the final multivariable logistic regression model achieved an AUROC of 0.807 and a PR-AUC of 0.168, higher than those of the age- and sex-only model. In the same-center longitudinal validation cohort, the final model achieved an AUROC of 0.795 and a PR-AUC of 0.216 for the primary incident carotid plaque outcome. The observed outcome rates increased across low-, intermediate-, and high-risk strata: 0.75%, 3.41%, and 13.9%, respectively. The high-risk stratum included 82 of 105 primary incident carotid plaque outcomes. Sensitivity analysis using Firth penalized logistic regression showed directionally consistent associations. Among adults under 50 years of age undergoing routine health examinations, a parsimonious lipid–metabolic model incorporating age, male sex, low-density lipoprotein cholesterol, systolic blood pressure, high-density lipoprotein cholesterol, and fasting glucose provided discrimination for prevalent carotid plaque status and stratified longitudinal incident plaque outcomes in a same-center repeated-examination cohort. This model provides an interpretable framework for early subclinical atherosclerosis risk communication and cardiometabolic risk management in health-examination settings.