Relationship between serum indirect bilirubin and prostate volume in patients with benign prostatic hyperplasia: a cross-sectional study

Abstract

Due to its anti-oxidative effects, bilirubin may protect against a spectrum of diseases. However, the role of bilirubin in patients with benign prostatic hyperplasia (BPH) is poorly explored. This study aimed to investigate the cross-sectional associations between serum indirect bilirubin (IBIL) and prostate volume (PV) in patients with BPH. The medical records of 722 BPH patients were retrospectively analyzed. Body mass index (BMI) was calculated as body weight (kg)/height (m)2. PV was obtained as height (cm) × width (cm) × length (cm) × π/6. Other biochemical indexes were measured by the automatic biochemical analyzer. A univariable linear regression analysis was performed to detect confounders. The IBIL-PV relationship was examined using unadjusted and covariate-adjusted regression models. Furthermore, a segmented linear regression was conducted to analyze the linear trend of IBIL levels and PV. Finally, the sensitivity analysis was stratified by BMI and low-density lipoprotein cholesterol (LDL-C) cutoffs. In this study, the mean age of the patients was 68 (range, 43-93) years. By univariable line regression test, we observed that PV was positively correlated with age, BMI, and LDL-C (β=0.113, 0.096, and 0.135, respectively). IBIL was negatively associated with PV in full adjusted model in men age ≤75 years (β=-1.01; 95% CI: -1.81, -0.22; P=0.01). A statistically significant inverse trend was observed between serum IBIL intervals and PV in patients aged ≤75 years (adjusted for age, BMI, and LDL-C, P for trend =0.015). In sensitivity analysis, significantly negative IBIL-PV relationship only existed in men with normal BMI (adjusted β=-1.328; 95% CI: -2.467, -0.190; P=0.022), overweight men (adjusted β=-1.296; 95% CI: -2.519, -0.074; P=0.038), and men with normal LDL-C level (adjusted β=-1.017; 95% CI: -1.869, -0.164; P=0.019). IBIL is negatively associated with PV in the non-obese population ≤75 years with normal LDL-C. These results suggest that higher serum IBIL possibly provides a degree of protection to BPH by mitigating oxidative stress (OS) related to aging and lipid peroxidation. Nevertheless, these preliminary findings from a single-center, retrospective study have limitations and need to be confirmed by future studies.