Gender Differences in Association Between Serum Indirect Bilirubin and Chronic Kidney Disease Risk: A Prospective Cohort Study in Northwest China

Background Current evidence remains limited regarding associations between serum indirect bilirubin (IBIL) levels and chronic kidney disease (CKD) risk, particularly in gender-stratified analyses. This study investigated the gender-specific relationship between serum IBIL and CKD incidence. Methods Using data from a prospective cohort in northwestern China, we followed 25,684 CKD-free participants. Cox proportional hazards models and restricted cubic spline regression were employed to assess IBIL-CKD associations. The predictive capacity of IBIL was evaluated through ROC curve analysis. Robustness of results was examined via subgroup and sensitivity analyses. Results Over 122,401.17 person-years of follow-up, 1,219 incident CKD cases emerged. Adjusted hazard ratios (95% CIs) for CKD were 0.794 (0.676–0.932) overall and 0.713 (0.589–0.862) among males. Area under the curve (AUC) values were 0.710 (0.704–0.715; p < 0.001) overall, 0.710 (0.703–0.718; p < 0.001) for males, and 0.679 (0.670–0.688; p < 0.001) for females. A linear dose-response pattern was observed exclusively in males. Results remained consistent across subgroup and sensitivity analyses. Conclusions Our findings demonstrate an inverse association between serum IBIL levels and CKD risk, with particular clinical relevance in male populations. These results suggest serum IBIL could function as a valuable biomarker for early CKD detection in males.