Cadmium or cadmium compounds and chronic kidney disease in workers and the general population: a systematic review

Background: Cadmium (Cd) is abundantly documented as a metal mainly affecting tubular function both in workers and in the general population indirectly exposed via the environment. Results from epidemiological studies linking Cd exposure and risk of progression to chronic kidney disease (CKD) are, however, conflicting. Objectives: To perform a systematic review of the association between Cd exposure and CKD. Methods: A systematic appraisal of publications found in MEDLINE (1946-2014), EMBASE (1974-2012) and an in-house database (1986-2013) was conducted. Additional studies were searched for by contacting experts and checking reference lists. Search terms used key and text words. No language restriction was applied. Cohort, case-control and case-series with follow-up including individual and objective assessment of occupational or environmental exposure were eligible. Studies were selected and data extracted by two independent reviewers using predefined forms. Study characteristics and results were extracted to structured tables. Synthesis was qualitative and results appraised with causality criteria. Results: Thirty-four exposed groups, totaling more than 3000 participants, were eligible. Overall, results disclosed no convincing evidence supporting a risk of progression to CKD in populations exposed to Cd. Lack of information about methods, risk of bias and heterogeneity were identified as limitations and precluded conducting a meta-analysis. Publication bias did not appear as a major problem. Conclusions: This qualitative systematic review does not support the contention that human exposure to Cd leads to progressive CKD.