To investigate the association between serum bilirubin and distal symmetrical polyneuropathy (DSPN) in Chinese patients with type 2 diabetes (T2D).

A total of 1800 inpatients with T2D (including 68 with 1-year follow-ups) were consecutively enrolled between June 2014 and March 2017. DSPN was diagnosed according to criteria recommended by the Toronto Diabetic Neuropathy Expert Group in 2010. Clinical data were retrospectively collected.

Patients with vs. without DSPN had low levels of serum total bilirubin (9.9±3.1μmol/L vs. 10.7±2.8μmol/L; P<0.01) and unconjugated bilirubin (6.7±2.2μmol/L vs. 7.3±2.1μmol/L; P<0.01), respectively. Patients in the lowest tertiles of bilirubin had the highest rates of DSPN and slowest nerve conduction velocities (NCVs). After multivariate adjustment, low levels of unconjugated bilirubin were a risk factor (OR: 0.696, 95% CI: 0.494–0.981; P=0.038, highest vs. lowest) for the presence of DSPN. Furthermore, in the 68 patients who had 1-year follow-ups, those with the lowest tertiles of serum bilirubin showed maximum deterioration in NCVs. These changes remained significant even after multivariate adjustment.

Low levels of serum bilirubin, especially unconjugated bilirubin, contributed to the presence and progression of DSPN in Chinese patients with T2D. Thus, serum unconjugated bilirubin may be used as an additional indicator of risk and progression of DSPN.