Abstract: Objective  To examine the association between serum bilirubin levels and bone mineral density (BMD), as well as osteoporosis (OP) in patients with type 2 diabetes mellitus(T2DM). Methods  A retrospective analysis was conducted in 1 514 T2DM patients  of Beijing Tongren Hospital, Capital Medical University. The age of the patients ranged from 50 to 94 years, with a mean age of (63.49±8.11) years. Serum total bilirubin (TBIL) and direct bilirubin (DBIL) levels were measured, and then was classified as Q1-Q4 groups based on quartiles. BMD was assessed by using dual-energy X-ray absorptiometry. OP was defined according to the diagnostic criteria of the World Health Organization, which indicated a T-score ≤ -2.5 for lumbar spine, total hip or femoral neck. Multivariable Logistic regression and linear regression models were used to analyze the relationship between serum bilirubin (TBIL and DBIL) levels and BMD, OP in T2DM patients. Results  There were significant differences in serum TBIL and DBIL levels between the OP and non-OP groups. After multivariable adjustment, the TBIL-Q4 group had a significantly higher prevalence of OP (OR=1.952, 95% CI: 1.041-3.659,P=0.037) and a significant decrease in lumbar spine BMD (β =-0.038, 95% CI :-0.072--0.004, P=0.027) compared to the TBIL-Q1 group. Compared to the DBIL-Q1 group, the DBIL-Q2 and DBIL-Q3 groups showed significant decreases in BMD at the femoral neck and total hip (P<0.05). Subgroup analysis showed that the impact of TBIL and DBIL on OP was more significant in the age ≤ 65 years and glycosylated hemoglobin (HbA1c) ≤ 7.0% groups. In female patients, TBIL levels were negatively correlated with lumbar spine BMD (β= -0.019, 95% CI:-0.034--0.005, P=0.009). Conclusion  Elevated bilirubin levels are associated with an increased prevalence of OP and decreased BMD, especially in subgroups of age ≤ 65 years and HbA1c ≤ 7.0%.

Key words: type 2 diabetes mellitus, total bilirubin, direct bilirubin, bone density, osteoporosis, bone metabolism