Higher serum total bilirubin concentration is associated with lower risk of renal insufficiency in an adult population.

BACKGROUND Chronic inflammation is proposed to play a central role in the pathogenesis of chronic kidney disease (CKD), and serum bilirubin has antioxidant and anti-inflammatory effects. We investigated the association between serum total bilirubin (Tb) concentration and renal function in an adult population. METHODS We conducted a cross-sectional study and collected anthropometric measurements, fasting blood tests, lifestyle habits and medical history of 3876 subjects attending a health examination. Renal insufficiency was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2) calculated by using the CKD-EPI equation. RESULTS Serum Tb concentrations were higher in subjects without renal insufficiency than in those with renal insufficiency. Multivariable linear regression analysis showed that Tb concentration was positively associated with eGFR after adjusting for important CKD risk factors (P=0.04). Multivariable logistic regression analysis also revealed that higher Tb concentration (each increment of 1.71 μmol/L) (0.1 mg/dL) was associated with a reduced risk of renal insufficiency: odds ratios were 0.94 (P=0.005) for men and 0.90 (P=0.015) for women, respectively. When subjects were divided into quartiles of serum Tb, multivariable-adjusted odds ratios for renal insufficiency comparing the fourth to the first Tb quartile were 0.49 (P=0.001) for men and 0.35 (P=0.003) for women. A stepwise exclusion of subjects, first those with possible liver disease and second, those with CKD stage 4 and 5, showed consistent results. CONCLUSION Higher serum Tb concentration was associated with lower risk of renal insufficiency, regardless of other conventional CKD risk factors.