Low serum bilirubin concentration is associated with coronary artery calcification (CAC)

BackgroundBilirubin is a potent antioxidant and previous studies have reported the relationship between low serum bilirubin concentration and atherosclerosis. The purpose of this study was to assess the correlation between serum bilirubin concentration and coronary artery calcification (CAC).MethodsThis study consisted of 637 participants and we evaluated the relationship between CAC score determined by multislice computed tomography and serum bilirubin concentration.ResultsAn inverse correlation was found between serum bilirubin concentration and log(CAC + 1) (r = −0.361, P < 0.0001). Multiple regression analysis also demonstrated that age (β = 0.261, P = 0.0125), systolic blood pressure (β = 0.153, P = 0.0237), uric acid (β = 0.126, P = 0.0441), estimated glomerular filtration rate (β = −0.139, P = 0.0416) and serum bilirubin concentration (β = −0.281, P < 0.0001) were independent determinants of log(CAC + 1). An increment of 1 μmol/L in serum bilirubin concentration was associated with 14% decrease in the odds for CAC score ≥400 after adjustment for several risk factors. Both age and SBP were also positively associated with CAC score ≥400, but the odds ratio for CAC score ≥400 was greater for every 1 μmol/L increment in serum bilirubin concentration than for every 1-year increment in age and 1-mmHg increment in SBP.ConclusionsLow serum bilirubin concentration is associated with coronary artery calcification. Serum bilirubin concentration can be measured easily in the clinical laboratory and applied in medical practice, and low serum bilirubin concentration would be useful as a provisional new risk factor of CAC.