Association of blood heavy metal concentrations with hearing loss: a systematic review and meta-analysis.

ABSTRACT

OBJECTIVES: This study aimed to assess the associations between blood heavy metal concentrations and hearing loss. STUDY DESIGN: This was a systematic review and meta-analysis. METHODS: A comprehensive literature search was performed using Embase, PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, Chinese Biomedical Literature, Wanfang and Weipu databases. Ten studies were included, and a random or fixed-effects model was used for the meta-analysis. Review Manager 5.4 software was used for data synthesis, and Stata 15.1 software was used for the publication bias and sensitivity analyses. RESULTS: Blood lead concentrations were significantly and substantially associated with hearing loss (mean difference (MD) = 1.14; 95% confidence interval [CI] = 0.03, 2.26; P = 0.04; I2 = 81%), and iron deficiency was significantly related to hearing loss (MD = -0.42; 95% CI = -0.66, -0.18; P = 0.12; I2 = 60%). CONCLUSIONS: These results suggest an association between blood heavy metal concentrations and hearing loss. However, there were limitations: confounding factors, lack of description for the specific methods of blinding and independent verification of case definition, limited sample size, Chinese publications comprising half of the primary data and the lack of assessment of the relationship between different blood heavy metal concentrations and the severity of hearing loss. Therefore, larger and well-designed prospective cohort studies are required for further exploration.