The nonlinear correlation between total bilirubin and lumbar spine bone mineral density in patients receiving maintenance hemodialysis.

Background: Patients receiving maintenance hemodialysis (MHD) are at increased risk of osteoporosis. The effects of bilirubin on bone metabolism vary among different disease populations. However, the relationship between total bilirubin (TBIL) and bone metabolism in MHD has not been investigated yet.

Materials and methods: This cross-sectional study included 122 MHD patients aged ≥ 18 years who underwent regular hemodialysis at the Blood Purification Center of Aerospace Central Hospital from April 2021 to April 2023. Blood sampling and bone mineral density (BMD) examinations were conducted. Multivariate linear regression, restricted cubic spline and subgroup analyses were performed to evaluate the association between TBIL and BMD.

Results: TBIL (correlation coefficient: 1.7 (0.17, 3.25); p = 0.04) was independently associated with BMD in the multivariate linear regression analysis. The results showed that BMD was nonlinearly related to TBIL in MHD patients, exhibiting a J shaped curve (p = 0.035). When plasma TBIL level < 0.64 mg/dL, there is an average increase of 5.3 (95% CI: 2.0 - 8.7; p = 0.002) g/cm² in BMD for every 1-unit increase in plasma TBIL level. The association between TBIL and BMD was not significant when the plasma TBIL level was ≥ 0.64 mg/dL.

Conclusion: The relationship between TBIL and BMD in MHD patients is J-shaped, with an inflection point of 0.64 mg/dL.