Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Department of Environmental and Occupational Health, The George Washington University Milken Institute School of Public Health, Washington, DC, USA.
Sci Total Environ. 2024 Jul 20;935:173387. doi: 10.1016/j.scitotenv.2024.173387. Epub 2024 May 23.
Research on metal-associated neurodegeneration has largely focused on single metals. Since metal exposures typically co-occur as combinations of both toxic and essential elements, a mixtures framework is important for identifying risk and protective factors. This study examined associations between toenail levels of an eight-metal mixture and attention and memory in men living in US Gulf states.
We measured toenail concentrations of toxic (arsenic, chromium, lead, and mercury) and essential (copper, manganese, selenium, and zinc) metals in 413 non-smoking men (23-69 years, 46 % Black) from the Gulf Long-Term Follow-Up (GuLF) Study. Sustained attention and working memory were assessed at the time of toenail sample collection using the continuous performance test (CPT) and digit span test (DST), respectively. Associations between toenail metal concentrations and performance on neurobehavioral tests were characterized using co-pollutant adjusted general linear models and Bayesian Kernel Machine Regression.
Adjusting for other metals, one interquartile range (IQR) increase in toenail chromium was associated with a 0.19 (95 % CI: -0.31, -0.07) point reduction in CPT D Prime score (poorer ability to discriminate test signals from noise). One IQR increase in toenail manganese was associated with a 0.20 (95 % CI, -0.41, 0.01) point reduction on the DST Reverse Count (fewer numbers recalled). Attention deficits were greater among Black participants compared to White participants for the same increase in toenail chromium concentrations. No evidence of synergistic interaction between metals or adverse effect of the overall metal mixture was observed for either outcome.
Our findings support existing studies of manganese-related memory deficits and are some of the first to show chromium related attention deficits in adults. Longitudinal study of cognitive decline is needed to verify chromium findings. Research into social and chemical co-exposures is also needed to explain racial differences in metal-associated neurobehavioral deficits observed in this study.
金属相关神经退行性疾病的研究主要集中在单一金属上。由于金属暴露通常以有毒和必需元素的混合物形式存在，因此混合物框架对于确定风险和保护因素很重要。本研究调查了美国海湾州男性脚趾甲中八种金属混合物水平与注意力和记忆力之间的关系。
我们在 Gulf Long-Term Follow-Up（GuLF）研究中测量了 413 名不吸烟男性（23-69 岁，46%为黑人）的脚趾甲中有毒（砷、铬、铅和汞）和必需（铜、锰、硒和锌）金属的浓度。在采集趾甲样本时，使用连续性能测试（CPT）和数字跨度测试（DST）分别评估了持续性注意力和工作记忆。使用协污染物调整的一般线性模型和贝叶斯核机器回归来描述脚趾甲金属浓度与神经行为测试表现之间的关系。
调整其他金属后，脚趾甲铬含量每增加一个四分位距（IQR），CPT D Prime 评分降低 0.19（95%CI：-0.31，-0.07）分（从噪声中辨别测试信号的能力下降）。脚趾甲锰含量每增加一个 IQR，DST 倒数（召回的数字较少）降低 0.20（95%CI，-0.41，0.01）分。对于相同的脚趾甲铬浓度增加，黑人参与者的注意力缺陷比白人参与者更为明显。对于这两种结果，都没有观察到金属之间的协同相互作用或整体金属混合物的不良影响的证据。
我们的研究结果支持现有的关于锰与记忆缺陷相关的研究，并首次表明在成年人中存在与铬相关的注意力缺陷。需要进行认知能力下降的纵向研究来验证铬的研究结果。还需要研究社会和化学共暴露，以解释本研究中观察到的与金属相关的神经行为缺陷的种族差异。
