Introduction: Bilirubin has antioxidant effects and may protect against atherosclerosis. Arterial stiffness in an independent cardiovascular risk factor for patients with hypertension. The purpose of this study was to investigate the association between bilirubin levels and arterial stiffness in hypertensive subjects.

Methods: We studied 293 consecutive patients with uncomplicated, never treated essential hypertension. Bilirubin concentrations were measured in all subjects who were then divided according to tertiles of bilirubin levels (113 patients with bilirubin concentrations <0.7 mg/dl, 82 patients with bilirubin concentrations between 0.7 and 1.02mg/dl and 98 patients with bilirubin concentrations >1.02 mg/dl). Arterial stiffness was evaluated by the measurement of carotid-femoral Pulse Wave Velocity (PWVc-f) and Augmentation Index (AIx).

Results: Using the ANOVA statistical analysis, AIx was significantly reduced with increasing bilirubin level tertiles (28.48±11.45, 27.26±12.11 and 23.98±13.60% respectively, P = 0.02). There was also a gradual reduction of PWVc-f from the lower to the higher tertiles (8.02±1.66, 7.83±1.36, and 7.55±1.17 m/s respectively, P = 0.06). Having AIx as a dependent variable, after adjustment for potential confounders, no independent association between bilirubin levels and AIx was observed.

Conclusion: Hypertensive subjects with elevated bilirubin concentrations have decreased values of arterial stiffness. Although an independent association was not observed, because bilirubin might act favorably through other determinants of arterial stiffness, the present finding reinforces the notion of a protective effect of bilirubin.