Serum total bilirubin is inversely associated with brachial-ankle pulse wave velocity in men with hypertension

Serum total bilirubin has been suggested to have the potential anti-inflammatory and antioxidant effects on the vasculature. This study was designed to investigate the association of bilirubin with brachial-ankle pulse wave velocity (baPWV), a marker of arterial stiffness and cardiovascular disease. Hypertensive male subjects (n = 2,361) were classified into groups according to the 50th, 75th, and 95th percentiles of baPWV value. Correlation and regression analysis were used to assess the relationship between baPWV and other variables. Hypertensive subjects with baPWV above the 50th, 75th, and 95th percentiles had a significantly lower bilirubin level than those with baPWV under them (0.97 ± 0.40 vs. 1.00 ± 0.41 mg/dl, P < 0.001; 0.95 ± 0.39 vs. 0.99 ± 0.41 mg/dl, P = 0.001; 0.92 ± 0.36 vs. 0.99 ± 0.42 mg/dl, P = 0.048, respectively). Bilirubin is inversely related to baPWV (R ² = 0.0032, P = 0.003) and C-reactive protein (CRP) (correlation coefficient = -0.13, P < 0.001). A 0.1 mg/dl increase in bilirubin was associated with a 19, 20, and 34 % reduced odds ratio for baPWV above the 50th, 75th, and 95th percentiles, respectively [odds ratio (OR) 0.77 (95 % confidence interval (CI) 0.62-0.95), P = 0.015; OR 0.80 (95 % CI 0.64-0.99), P = 0.044; OR 0.68 (95 % CI 0.45-1.00), P = 0.048, respectively] after adjustment for several variables. This study demonstrates an independent inverse association between bilirubin and baPWV in hypertensive men. Additionally, reduced CRP may be one of mediators on the mechanisms how bilirubin reduces baPWV.