Association between serum bilirubin levels and decline in estimated glomerular filtration rate among patients with type 2 diabetes

Aims: Studies indicate that elevated serum total bilirubin (TBil) levels are associated with lower risk of diabetic kidney disease (DKD). Few studies examined the associations of direct bilirubin (DBil) and indirect bilirubin (IBil) with the development of DKD. Methods: Type 2 diabetes patients (n = 2,958) with estimated glomerular filtration (eGFR) >= 60 ml min(-1) 1.73 m(-2) from the Dongfeng-Tongji cohort were selected and followed up for 5 years. Development of DKD was defined as decline in eGFR >= 30% during follow-up. Generalize linear model was used to assess the associations of bilirubin levels with DKD development. Results: Compared with those in the first tertile of serum TBil, the relative risks (RRs) and 95% confidence intervals (CIs) of incident eGFR decline for tertile 2 to 3 were 0.83 (0.64-1.09) and 0.74 (0.56-0.98), P-trend = 0.04. The counterpart RRs (95% CIs) in IBil were 0.74 (0.57-0.97) and 0.75 (0.57-0.98), P-trend = 0.04. No significant associations were observed in DBil. Moreover, TBil and IBil interacted with smoking, the bilirubin-DKD associations were evident in ever smokers. Conclusions: Our findings suggest that elevation of serum TBil or IBil levels are independent protective factors for development of DKD, particularly in smokers. (C) 2016 Elsevier Inc. All rights reserved.