Red Blood Cell-to-Red Cell Distribution Width Ratio (RBC/RDW) Associated With Early Cardiovascular Risk in Young Mexican Adults With Low High-Density Lipoprotein Cholesterol (HDL-c) and Elevated Triglycerides.

Emerging adulthood represents a critical stage in the early development of cardiovascular risk, characterized by the silent accumulation of metabolic and inflammatory alterations before the onset of overt cardiovascular disease (CVD). This study evaluated anthropometric, hematological, and immunoinflammatory alterations associated with low high-density lipoprotein cholesterol (HDL-c) and elevated triacylglycerides (TAG) in young adults and determined the diagnostic utility of blood count-derived indices for identifying early cardiovascular risk (ECR). In total, 1,296 young adults were classified according to lipid phenotype as normal, low HDL-c, high TAG, or low HDL-c + high TAG. Lipid abnormalities were identified in 34% of participants and were associated with increased BMI, blood pressure, and uric acid concentrations. Phenotypes with elevated TAG exhibited a higher prevalence of prehypertension (Pre-HTN) and ECR. The systemic inflammation response index (SIRI) and aggregate index of systemic inflammation (AISI) were elevated in dyslipidemic phenotypes, suggesting the presence of subclinical meta-inflammation from early adulthood. Erythrocyte indices derived from red cell distribution width (RDW) also showed alterations associated with cardiometabolic dysfunction. In particular, the red blood cell-to-RDW ratio (RBC/RDW) was associated with elevated TAG and demonstrated complementary diagnostic utility for ECR detection. Unsupervised multivariate analyses identified AISI and RBC/RDW as being associated with sex, dyslipidemia, and a higher prevalence of ECR. Receiver operating characteristic analysis demonstrated that RBC/RDW, combined with sex and BMI, identified ECR with high diagnostic performance (area under the curve = 0.87). These findings indicate that young adults without diagnosed metabolic or CVD already exhibit detectable hematological and immunoinflammatory alterations. Readily available and low-cost indices such as RBC/RDW, together with sex and BMI, may therefore contribute to the early identification of subclinical cardiovascular risk during emerging adulthood. However, the cross-sectional design of this study indicates the need for prospective longitudinal studies to validate its usefulness in routine screening and risk prediction.