Associations of Mixed-Metal Exposure with Incident Chronic Kidney Disease in an Occupational Population: A Nested Case–Control Study

Long-term occupational exposure to multiple metals in mining environments may be associated with chronic kidney disease (CKD), but the associations between mixed metal exposure and CKD remain insufficiently characterized. A nested case–control study was conducted within the Jinchang Cohort, established in 2011 among workers with long-term multi-metal exposure at Jinchuan Group Co., Ltd. Among eligible cohort members, 1000 incident CKD cases identified at the third follow-up were compared with 1000 controls randomly selected from non-diseased cohort members. Bayesian Kernel Machine Regression (BKMR) was used to assess the joint association of mixed metal exposure with CKD, while multivariable logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) for individual metals. Restricted cubic splines (RCS) were used to evaluate potential nonlinear dose–response relationships. Mixed-metal exposure showed an exposure-dependent pattern, with the estimated association shifting from negative at lower mixture levels to positive at higher exposure levels. Li, Al, Cr, and Ni showed positive associations with CKD, whereas Zn and Se showed inverse associations.