Association between seminal plasma zinc level and asthenozoospermia: a meta-analysis study

Zinc is proposed to have an important role in the morphology, viability and motility of spermatozoa. There are inconsistent reports on the association between seminal plasma zinc concentration and male infertility. For this purpose, papers reporting the level of seminal zinc among asthenozoospermic groups were selected and used for further analysis. This meta-analysis of previous published studies was performed to obtain more precise information on the association between seminal plasma zinc and asthenozoospermia. Relevant studies for inclusion were identified after preliminary investigation of research papers published on electronic databases up to February 2015. Eight reports and 475 subjects were finally included in the meta-analysis. In the overall analysis, a statistically significant reduction in seminal plasma zinc concentrations was observed in asthenozoospermic infertile men. Random-effects method was used to evaluate the summary effect size due to the presence of significant heterogeneity. The effect of zinc on asthenozoospermia was significant (Hedge's G effect size = -0.506, 95% confidence interval (95% CI): -0.998 to -0.014, P = 0.044). Taken together, despite of significant statistical heterogeneity between studies, our findings were indicative of significant association between zinc concentration and asthenozoospermia. In conclusion, the meta-analysis suggests that seminal plasma zinc concentration is negatively associated with male infertility.