Total serum bilirubin and 8-year incident type 2 diabetes mellitus: The Korean Genome and Epidemiology Study

Aim: In this study, the impact of serum bilirubin on new-onset type 2 diabetes mellitus (T2DM) in Korean adults was investigated. Methods: Data were obtained from the Korean Genome and Epidemiology Study (KoGES), a population-based prospective cohort study. The study enrolled 8650 adults (4015 men and 4635 women), aged 40 to 69 years, who underwent a mean follow-up of 8.4 years. The study population was divided into quartiles (Q) of serum bilirubin levels, with cut-off points at 0.46, 0.61 and 0.82 mg/dL for men, and 0.35, 0.47 and 0.61 mg/dL for women. T2DM was defined based on the following data: fasting blood glucose ≥ 7.0 mmol/L, HbA_1c level ≥ 6.5% or 2-h plasma glucose ≥ 11.1 mmol/L during a 75-g oral glucose tolerance test. Results: Over the mean 8.4-year follow-up, 786 participants (9.1%) developed T2DM. Compared with Q1, the odds ratios (ORs) and 95% confidence intervals (CIs) for T2DM incidence were 0.52 (0.36–0.74) in men and 0.56 (0.38–0.83) in women aged ≥50 years, respectively, in the highest Q group after adjusting for possible confounding factors. These significant results persisted in those with impaired glucose tolerance and impaired fasting glucose. Conclusion: The results of this study reveal a protective role for serum total bilirubin on new-onset T2DM in Korean men and women. In addition, serum total bilirubin had favourable effects on new-onset T2DM in those with impaired glucose tolerance and impaired fasting glucose.