Vinnikov Denis, Syurin Sergei
al-Farabi Kazakh National University, 71 al-Farabi avenue, Almaty, 050040, Kazakhstan.
Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya street, Moscow, 117198, Russian Federation.
BMC Public Health. 2024 Dec 19;24(1):3545. doi: 10.1186/s12889-024-21119-y.
Reproductive effects of chronic exposure to nickel (Ni), including sperm quality, have been a matter of debate given that published studies yielded contrasting results. We have, therefore, planned to systematically search and analyze medical literature with the aim to ascertain the association of exposure to nickel with the sperm quality in humans.
We systematically searched Pubmed, Scopus and Embase for studies reporting the association of Ni with the sperm quality in humans with no time or language limits and used PRISMA to report the findings. The risk of bias was assessed using JBI critical appraisal checklist and SIGN tool. Because the reported effects were no coherent, meta-analysis was not possible.
All included studies were observational and planned to test the effect of a group of trace elements, but not Ni alone. We identified and included 19 studies from 23 publications, published from 12 countries, which assessed sperm quality, sperm DNA damage and sperm metabolome. Ni was quantified in blood, semen plasma, spermatozoa and urine. Sixteen included cross-sectional studies were of acceptable quality, whereas three more case-control reports were of poor quality. Multivariate models were reported in only eight studies. Overall, studies were inconsistent in the direction of effect, when elevated Ni was not associated with the outcome (N = 8 studies), or some association was present (N = 11 studies). In the latter, 9 studies yielded elevated risk and 2 studies exhibited protective effect. Only one report was in an occupationally exposed population with some association with tail defects, but present in both welders and controls.
Existing evidence from the studies in humans is inconsistent and does not confirm a clear adverse effect of higher Ni concentrations in blood, urine or semen on the sperm quality. Robust methodology must be a key issue in the future studies. Studies with more powerful evidence, such as cohort or experimental reports are needed.
长期接触镍（Ni）对生殖的影响，包括精子质量，一直存在争议，因为已发表的研究结果相互矛盾。因此，我们计划系统检索和分析医学文献，以确定镍暴露与人类精子质量之间的关联。
我们系统检索了PubMed、Scopus和Embase数据库，以查找报告镍与人类精子质量关联的研究，无时间或语言限制，并使用PRISMA报告研究结果。使用JBI批判性评价清单和SIGN工具评估偏倚风险。由于报告的效应不一致，无法进行荟萃分析。
所有纳入的研究均为观察性研究，旨在测试一组微量元素的效应，而非单独测试镍的效应。我们从12个国家发表的23篇文献中识别并纳入了19项研究，这些研究评估了精子质量、精子DNA损伤和精子代谢组。在血液、精液、精子和尿液中对镍进行了定量分析。纳入的16项横断面研究质量可接受，而另外3项病例对照报告质量较差。只有8项研究报告了多变量模型。总体而言，当镍升高与结果无关联时（N = 8项研究），或存在某种关联时（N = 11项研究），研究在效应方向上不一致。在后者中，9项研究显示风险升高，2项研究显示保护作用。只有一份报告针对职业暴露人群，发现与尾部缺陷有某种关联，但在焊工和对照组中均存在。
来自人类研究的现有证据不一致，并未证实血液、尿液或精液中较高镍浓度对精子质量有明确的不良影响。强有力的方法学必须是未来研究的关键问题。需要有更有力证据的研究，如队列研究或实验报告。
