We examined the potential impact of demographic characteristics on the independent leptin-metabolic cardiovascular risk factor and leptin-endothelial activation relationships in black and white patients with RA. Leptin concentrations and those of endothelial activation molecules including soluble E-selectin, vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 were measured in 217 RA patients (51.6% black). We determined associations in potential confounder and mediator-adjusted mixed regression models. No independent associations between leptin concentrations and cardiovascular risk were present in all patients and either women and men or black and white patients. However, age impacted on several leptin-cardiovascular risk relations (interaction P < 0.05). In patients aged <50 years (lower quartile), after but not before adjustment for waist circumference and body mass index in addition to other confounders, leptin concentrations associated with overall endothelial activation as estimated by an SD (z) score of endothelial activation molecule concentrations (partial R = 0.341, P = 0.04). In patients aged 50-58 years (second quartile), leptin concentrations related to those of HDL cholesterol (partial R = -0.365, P = 0.01) and total cholesterol-HDL cholesterol ratio (partial R = 0.299, P = 0.04), and in those aged 59-63 years (third quartile), paradoxically related to low systolic and mean blood pressure (partial R = -0.438, P = 0.005 and partial R = -0.370, P = 0.02, respectively). Patients with RA aged <50 years experience an independent adiposity-driven leptin-endothelial activation relationship in the absence of leptin-metabolic risk factor associations. Young but not older patients with RA may sustain obesity-induced endothelial activation that is directly mediated by leptin.