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.

背景：已有大量研究证实，镉（Cadmium, Cd）作为一种金属污染物，主要影响职业暴露人群及经环境途径间接暴露的普通人群的肾小管功能。然而，现有流行病学研究关于镉暴露与慢性肾脏病（Chronic Kidney Disease, CKD）进展风险的关联结果却存在争议。
研究目的：系统评价镉暴露与慢性肾脏病之间的关联。
研究方法：系统检索MEDLINE数据库（1946–2014）、EMBASE数据库（1974–2012）及内部自建数据库（1986–2013）收录的文献，并通过联系领域专家、核查参考文献列表补充检索相关研究。检索策略同时采用主题词与自由词，未设置语言限制。纳入标准包括：设有随访的队列研究、病例对照研究及病例系列研究，且需包含对职业或环境暴露的个体化、客观评估。由两名独立评价者采用预先设计的数据提取表完成文献筛选与数据提取，将研究特征及结果提取至结构化表格中。研究采用定性综合法进行结果整合，并依据因果关系判定标准对研究结果进行评价。
研究结果：共纳入34个暴露组，总参与者超过3000例。整体而言，未发现确凿证据支持镉暴露人群存在进展为慢性肾脏病的风险。本研究存在的局限性包括：研究方法学信息缺失、偏倚风险及研究间异质性，上述问题导致无法开展Meta分析。未发现发表偏倚为主要问题。
结论：本项定性系统评价不支持人类镉暴露可导致慢性肾脏病进展这一论点。