The Relationship between Plasma Al Levels and Multi-domain Cognitive Performance among In-service Aluminum-exposed Workers at the SH Aluminum Factory in China: A Cross-sectional Study

LncRNA 51A: A promising diagnostic biomarker for assessing cognitive decline in occupationally exposed aluminum workers

OBJECTIVE

To assess the diagnostic utility of lncRNA 51 A in detecting cognitive decline among aluminum-exposed workers occupationally.

METHODS

921 male workers from an aluminum manufacturing facility underwent cognitive assessments, measurement of plasma aluminum levels and quantification of lncRNA 51 A levels. Receiver Operating Characteristic (ROC) curves were constructed to assess the diagnostic potential of lncRNA 51 A. Bayesian network model was utilized to predict the likelihood of cognitive decline among the study population.

RESULTS

Significant differences in lncRNA 51 A levels, plasma aluminum concentration and MMSE scores were observed between cognitive normal and decline groups. The lncRNA 51 A expression was negatively correlated with MMSE scores. The area under the curve (AUC) was 0.894, with 89.3 % sensitivity and 73.9 % specificity. The Bayesian network model indicated varying probabilities of cognitive decline based on lncRNA 51 A expression levels.

CONCLUSION

Plasma lncRNA 51 A shows potential as an excellent biomarker for cognitive decline diagnosis in aluminum-exposed workers.

LNC000152 Mediates Aluminum-Induced Proliferation of Reactive Astrocytes

Aluminum is a metal element with significant neurotoxicity, and there is a substantial correlation between aluminum exposure and cognitive dysfunction. Glial fibrillary acidic protein (GFAP) is widely used as a marker of reactive astrocyte proliferation in response to pathological injury of the central nervous system. Studies of various neurodegenerative diseases have confirmed that the expression changes in GFAP are associated with nerve injury. We investigated the role of LNC000152 in the aluminum-induced reactive proliferation of astrocytes. By establishing two aluminum-exposed cell models of rat primary astrocytes and CTX-TNA2 cell lines, we examined the expression of LNC000152 and GFAP and detected cell proliferation with EdU and cell cycle changes with flow cytometry. The role of aluminum in promoting glial cell proliferation was verified; the expression levels of LNC000152 and GFAP increased with the concentration of aluminum exposure. Intervention of LNC000152 expression by siRNA technology revealed that LNC000152 affected glial cell responsive proliferation by influencing GFAP expression. These results suggest that LNC000152 plays a role in the reactive proliferation of astrocytes induced by aluminum.

METTL3-mediated m6A RNA methylation was involved in aluminum-induced neurotoxicity

Aluminum (Al) exposure has been linked to the development of a variety of neurodegenerative diseases. However, whether m6A RNA methylation participated in Al-induced neurotoxicity remain to be defined. In this study, mice were administrated with aluminum-lactate at dose of 220 mg/kg. bw by gavage for 3 months. Meanwhile, the primary hippocampal neurons were isolated and treated with 0, 50, 100, 150 μM aluminum-lactate, respectively for 7 days. Al exposure caused neuronal shrinkage, decreased Nissl bodies, and increased apoptosis. In accordance, in vitro studies also showed that Al exposure led to neuronal apoptosis in a dose-dependent manner, together with the decline in m6A RNA methylation levels. Moreover, the mRNA expression of Mettl3, Mettl14, Fto, and Ythdf2 were decreased upon Al exposure. Notably, the protein expression of METTL3 was dramatically down-regulated by 42% and 35% in Al-treated mice and neurons, suggesting METTL3 might exert a crucial role in Al-induced neurotoxicity. We next established a mouse model with hippocampus-specific overexpressing of Mettl3 gene to confirm the regulatory role of RNA methylation and found that METTL3 overexpression relieved the neurological injury induced by Al. The integrated MeRIP-seq and RNA-seq analysis elucidated that 631 genes were differentially expressed at both m6A RNA methylation and mRNA expression. Notably, EGFR tyrosine kinase inhibitor resistance, Rap1 signaling pathway, protein digestion and absorption might be involved in Al-induced neurotoxicity. Moreover, VEGFA, Thbs1, and PDGFB might be the central molecules. Collectively, our findings provide the novel sight into the role of m6A RNA methylation in neurodegenerative disease induced by Al.

Aluminum exposure induces central nervous system impairment via activating NLRP3-medicated pyroptosis pathway

PURPOSE

Aluminum is an environmental toxicant whose long-term exposure is closely associated with nervous system impairment. This study mainly investigated neurological impairment induced by subchronic aluminum exposure via activating NLRP3-medicated pyroptosis pathway.

METHODS

In vivo, Kunming mice were exposed to AlCl3 (30.3 mg/kg, 101 mg/kg and 303 mg/kg) via drinking water for 3 months, and administered with Rsv (100 mg/kg) by gavage for 1 month. Cognitive impairment was assessed by Morris water maze test, and pathological injury was detected via H&E staining. BBB integrity, pyroptosis and neuroinflammation were evaluated through western blotting and immunofluorescence methods. In vitro, BV2 microglia was treated with AlCl3 (0.5 mM, 1 mM and 2 mM) to sensitize pyroptosis pathway. The protein interaction was verified by co-immunoprecipitation, and neuronal damage was estimated via a conditioned medium co-culture system with BV2 and TH22 cells.

RESULTS

Our results showed that AlCl3 induced mice memory disorder, BBB destruction, and pathological injury. Besides, aluminum caused glial activation, sensitized DDX3X-NLRP3 pyroptosis pathway, released cytokines IL-1β and IL-18, initiating neuroinflammation. BV2 microglia treated with AlCl3 emerged hyperactivation and pyroptotic death, and Ddx3x knockdown inhibited pyroptosis signaling pathway. DDX3X acted as a live-or-die checkpoint in stressed cells by regulating NLRP3 inflammasome and G3BP1 stress granules. Furthermore, aluminum-activated microglia had an adverse effect on co-cultured neurons and destroyed nervous system homeostasis.

CONCLUSION

Aluminum exposure could induce pyroptosis and neurotoxicity. DDX3X determined live or die via selectively regulating pro-survival stress granules or pro-death NLRP3 inflammasome. Excessive activation of microglia might damage neurons and aggravate nerve injury.

Advances in Genetics and Epigenetics of Developmental Coordination Disorder in Children

Developmental coordination disorder (DCD) is a developmental disorder characterized by impaired motor coordination, often co-occurring with attention deficit disorder, autism spectrum disorders, and other psychological and behavioural conditions. The aetiology of DCD is believed to involve brain changes and environmental factors, with genetics also playing a role in its pathogenesis. Recent research has identified several candidate genes and genetic factors associated with motor impairment, including deletions, copy number variations, single nucleotide polymorphisms, and epigenetic modifications. This review provides an overview of the current knowledge in genetic research on DCD, highlighting the importance of continued research into the underlying genetic mechanisms. While evidence suggests a genetic contribution to DCD, the evidence is still in its early stages, and much of the current evidence is based on studies of co-occurring conditions. Further research to better understand the genetic basis of DCD could have important implications for diagnosis, treatment, and our understanding of the condition's aetiology.

Interaction between aluminum exposure and ApoEε4 gene on cognitive function of in-service workers

The occurrence and development of cognitive impairment, the early stage of AD, may be affected both by factors of environmental (aluminum exposure) and genetic (ApoEε4 gene). But whether there is an interaction between the two factors on cognitive function is still unknown. To explore the interaction between the two factors on cognitive function of in-service workers. A total of 1121 in-service workers in a large aluminum factory were investigated in Shanxi Province. Cognitive function was assessed by the Mini-mental State Examination (MMSE), the clock-drawing test (CDT), the Digit Span Test (DST, including DSFT and DSBT), the fuld object memory evaluation (FOM), and the verbal fluency task (VFT). The plasma-Al (p-Al) concentrations were measured by inductively coupled plasma-mass spectrometry (ICP-MS) as an internal exposure indicator, and the participants were divided into four Al exposure groups according to the quartile of p-Al concentrations, namely Q1, Q2, Q3, and Q4. ApoE genotype was determined by Ligase Detection Reaction (LDR). The multiplicative model was fitted using non-conditional logistic regression and additive model was fitted using crossover analysis to analyze the interaction between p-Al concentrations and the ApoEε4 gene. Finally, a dose-response relationship between p-Al concentrations and cognitive impairment was observed, with the p-Al concentrations increased, cognitive function performance gradually becomes worse (P_trend＜0.05), and the risk of cognitive impairment gradually increases (P_trend＜0.05), mainly in executive/visuospatial impairment, auditory memory impairment (particularly the working memory impairment). And ApoEε4 gene may be a risk factor for cognitive impairment, while no association between the ApoEε2 gene and cognitive impairment is observed. Additionally, an additive but no multiplicative interaction between p-Al concentrations and ApoEε4 gene is observed, and when the two factors work together, the risk of cognitive impairment further increased, of which 44.2% can be attributed to the interaction effect.

Simultaneous effects of aluminum exposure on the homeostasis of essential metal content in rat brain and perturbation of gut microbiota

The theory of the brain-gut axis has confirmed that gut microbiota and metabolites are involved in the progression of neurodegenerative diseases through multiple pathways. However, few studies have highlighted the role of gut microbiota in cognitive impairment induced by aluminum (Al) exposure and its correlations with the homeostasis of essential metal content in the brain. To explore the relationship between alterations in the content of essential metals in the brain and relative abundance changes in gut microbiota induced by Al exposure, the Al, zinc (Zn), copper (Cu), iron (Fe), chromium (Cr), manganese (Mn), and cobalt (Co) content level in the hippocampus, olfactory bulb, and midbrain tissue were measured by inductively coupled plasma mass spectrometry (ICP-MS) methods after Al maltolate was intraperitoneally injected every other day for exposed groups. Then the unsupervised principal coordinates analysis (PCoA) and linear discriminant analysis effect size (LEfSe) were used to analyze the relative abundance of the gut microbiota community and the structure of the gut microbiome. Finally, the correlations between gut microbiota composition and essential metal content in the different exposure groups were explored by using the Pearson correlation coefficient method. Based on the results, we indicated that the content of Al in the hippocampus, olfactory bulb, and midbrain tissue was increased and then decreased with the increasing exposure duration, with peaks occurring between 14 and 30 days. Concomitantly, Al-exposure decreased the Zn, Fe, and Mn levels in these tissues. 16 S rRNA gene sequencing results indicated that significant differences in the intestinal microbial community structure at the phylum, family, and genus levels were found in the Day 90 exposed group compared with the Day 7 exposed group. Ten enriched species in the exposed group were identified as markers at the three levels. Furthermore, ten bacteria at the genus level were identified to have a significantly strong correlation (r = 0.70-0.90) with Fe, Zn, Mn, and Co.

Effect of the Reelin-Dab1 signaling pathway on the abnormal metabolism of Aβ protein induced by aluminum

Aluminum (Al) is a common neurotoxic element that can exacerbate intracellular β-amyloid (Aβ) deposition. Reelin is a highly conserved extracellular glycoprotein that is involved in intracellular Aβ deposition. However, the action of Reelin on aluminum-induced Aβ deposition is not fully understood. Here, we investigated the effects of the Reelin-Dab1 signaling pathway on Aβ deposition in aluminum maltol (Al(mal)₃) exposure in rat pheochromocytoma-derived cells (PC12). Our results showed that Al(mal)₃ exposure decreased activity of PC12, increased expression of Aβ₄₂, and decreased expression of Aβ₄₀. Moreover, Al(mal)₃ exposure in PC12 induced Reelin-Dab1 signaling pathway-associated proteins changed, decreased expression of Reelin and Dab1, and increased expression of pdab1. Moreover, the expression of Reelin, Dab1, and Aβ₄₀ was found to be elevated in PC12 exposed to Al(mal)₃ and corticosterone compared to those exposed to Al(mal)₃. Also, the expression of Reelin, Dab1, and Aβ₄₀ was found to be depressed in PC12 exposed to Al(mal)₃ and streptozotocin compared with cells exposed to Al(mal)₃ alone. These results suggested that Al(mal)₃ inhibits the expression of the Reelin-Dab1 signaling pathway, promoting Aβ deposition. Thus, our findings provided important evidence to better understand how the Reelin-Dab1 signaling pathway may be a potential mechanism of Aβ deposition induced by aluminum.

Associations Between Plasma Metals and Cognitive Function in People Aged 60 and Above

The objective of the study was to explore the relationship between the plasma levels of 22 metals and cognition status in older adults aged 60 years and above. A cross-sectional survey was conducted between 2018 and 2019. Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the concentrations of metals, and a mini-mental state examination (MMSE) questionnaire was used to estimate the cognition status of the elderly. Based on the years of education and MMSE scores, the participants were separated into the normal and impaired cognition groups. Lasso regression, logistic regression, and restricted cubic spline models were used to explore the relationship between the metals and cognitive status. A total of 1667 subjects were included in the study, and 333 (19.97%) of the participants had impaired cognition. Then, 12 metals, including Al, Fe, Ni, Cu, As, Se, Rb, Sr, Mo, Cd, Sn, and Sb were selected by lasso regression. Before the multivariate adjustment, Al and Cu were associated with the risk of increasing cognitive impairment (OR = 1.756, 95% CI: 1.166-2.646, P = 0.007; OR = 1.519, 95% CI: 1.050-2.197, P = 0.026, respectively). By contrast, Rb was associated with a decrease in the risk of cognitive impairment (OR = 0.626, 95% CI: 0.427-0.918, P = 0.017), but Cd was significantly associated with an increase in this risk (OR = 1.456, 95% CI: 1.003-2.114, P = 0.048). After multivariate adjustment, only Al (OR = 1.533, 95% CI: 1.000-2.350, P = 0.050) maintained a borderline difference with the risk of cognitive impairment. A significant positive correlation was found between the risk of cognitive impairment and Al, Cu, and Cd, contrary to the negative correlation found with Rb.

Blood glucose mediated the effects of cognitive function impairment related to aluminum exposure in Chinese aluminum smelting workers

OBJECT

To explore the effects of occupational aluminum exposure on workers' cognitive function and blood glucose concentration, and to analyze whether blood glucose concentration can mediate the cognitive changes caused by aluminum.

METHOD

Our study recruited 375 workers from an aluminum factory in northern China. We collected the fasting elbow venous blood of the workers, measured their fasting blood glucose concentration (FBG), and used ICP-MS to determine plasma aluminum concentration (P-Al) as an indicator of internal exposure. The Montreal Cognitive Assessment (MoCA), was used to assess the cognitive function of workers. Generalized linear model was used to analyze the association of P-Al with cognitive function and blood glucose concentration, and the restricted cubic spline model was used to fit the dose-response relationship. We also conducted a mediation effect analysis.

RESULT

We observed the dose-response relationship, that is, as the P-Al increased, sum of MoCA, visuospatial/executive, naming, language, and abstraction scores decreased, and the blood glucose concentration increased. For every e-fold increase in P-Al, sum of MoCA, visuospatial/executive, naming, language, and abstraction scores decreased by 0.328 points, 0.120 points, 0.059 points, 0.060 points, and 0.083 points, respectively, and FBG rose by 0.109 mmol/L. FBG has a significant mediating effect between P-Al and sum of MoCA (P for mediator=0.042), and it could explain 10.7% of the effect of cognitive level related to P-Al.

CONCLUSION

Occupational aluminum exposure negatively affected the cognitive function of workers and positively affected FBG. FBG may partially explain the impact of occupational aluminum exposure on workers' cognitive function.

Blood pressure mediated the effects of cognitive function impairment related to aluminum exposure in Chinese aluminum smelting workers

OBJECTIVES

The aim of this study is to investigate the effects that the Al on blood pressure and the effect of hypertension in aluminum-induced cognitive impairment in electrolytic aluminum worker.

METHODS

The study was conducted 392 male aluminum electrolytic workers in an aluminum plant of China. The concentration of alumina dust in the air of the electrolytic aluminum workshop is 1.07mg/m3-2.13mg/m3. According to the Permissible concentration-Time Weighted Average of alumina dust is 4mg/ m3, which does not exceed the standard. The blood pressure of the workers was measured. The plasma aluminum concentration of workers was determined by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Cognitive functions were measured using MMSE (Mini-Mental State Examination), VFT (Verbal Fluency Test), ATIME (Average Reaction Time), FOM (Fuld Object Memory Evaluation), DST (Digit Span Test), CDT (Clock Drawing Test) scales. Modified Poisson regression was used to analyze the risk of hypertension and cognitive impairment with different plasma aluminum concentrations. Generalized linear regression model was used to analyze the relationship between aluminum and cognitive function, blood pressure and cognitive function. Causal Mediation Analysis was used to analyze the mediation effect of blood press in aluminum-induced cognitive impairment.

RESULTS

Plasma aluminum appeared to be a risk factor for hypertension (PR (prevalence ratio) = 1.630, 95%-CI (confidence interval): 1.103 to 2.407), systolic blood pressure (PR = 1.578, 95%-CI: 1.038 to 2.399) and diastolic blood pressure (PR = 1.842, 95%-CI: 1.153 to 2.944). And plasma aluminum increased by e-fold, the scores of MMSE and VFT decreased by 0.630 and 2.231 units respectively and the time of ATIME increased by 0.029 units. In addition, generalized linear regression model showed that blood press was negatively correlated with the scores of MMSE and VFT. Finally, causal Mediation Analysis showed that hypertension was a part of the mediating factors of aluminum-induced decline in MMSE score, and the mediating effects was 16.300% (7.100%, 33.200%). In addition, hypertension was a part of the mediating factors of aluminum-induced decline in VFT score, and the mediating effects was 9.400% (2.600%, 29.000%) CONCLUSION: Occupational aluminum exposure increases the risk of hypertension and cognitive impairment. And hypertension may be a mediating factor of cognitive impairment caused by aluminum exposure.

Association of both prenatal and early childhood multiple metals exposure with neurodevelopment in infant: A prospective cohort study

BACKGROUND

Impaired neurodevelopment of children has become a growing public concern; however, the associations between metals exposure and neurocognitive function have remained largely unknown.

OBJECTIVES

We systematically evaluated the associations of multiple metals exposure during pregnancy and childhood on the neurodevelopment of children aged 2-3 years.

METHODS

We measured 22 metals in the serum and urine among703 mother-child pairs from the Guangxi Birth Cohort Study. The neurocognitive development of children was assessed by the Gesell Development Diagnosis Scale (GDDS; Chinese version). Multiple linear regression models were used to evaluate the relationship between the metals (selected by elastic net regression) and the outcomes. The Bayesian kernel machine regression (BKMR) was used to evaluate the possible joint effect between the multiple metal mixture and the outcomes.

RESULTS

Prenatal aluminum (Al) exposure was negatively associated with the fine motor developmental quotient (DQ) (β = -1.545, 95%CI: 2.231, -0.859), adaption DQ (β = -1.182, 95%CI: 1.632, -0.732), language DQ (β = -1.284, 95% CI: 1.758, -0.809), and social DQ (β = -1.729, 95% CI: 2.406, -1.052) in the multi-metal model. Prenatal cadmium (Cd) exposure was negatively associated with gross motor DQ (β = -2.524, 95% CI: 4.060, -0.988), while postpartum Cd exposure was negatively associated with language DQ (β = -1.678, 95% CI: 3.227, -0.129). In stratified analyses, infants of different sexes had different sensitivities to metal exposure, and neurobehavioral development was more significantly affected by metal exposure in the first and second trimester. BKMR analysis revealed a negative joint effect of the Al, Cd, and selenium (Se) on the language DQ score; postpartum Cd exposure played a major role in this relationship.

CONCLUSION

Prenatal exposure to Al, Ba, Cd, molybdenum (Mo), lead (Pb), antimony (Sb), and strontium (Sr), and postpartum exposure to cobalt (Co), Cd, stannum (Sn), iron (Fe), nickel (Ni), and Se are associated with neurological development of infants. The first and second trimester might be the most sensitive period when metal exposure affects neurodevelopment.

The association between blood lymphocyte NMDAR, group I mGluRs and cognitive function changes in occupationally aluminum-exposed workers and verification in rats

BACKGROUND

Many studies have shown that occupational aluminum (Al) exposure could affect the cognitive functions of workers and cause mild cognitive impairment (MCI). Glutamate receptors (GluRs) play an important role in learning and memory functions.

METHODS

352 workers in a large Al production enterprise were investigated in this research. MMSE, CDT, DST, VFT, FOM were used to evaluate the cognitive functions of workers. Plasma Al levels as exposure indices were measured by Graphite Furnace Atomic Absorption Method (GFAAS). The expression of GluRs was measured by ELISA. Cognitive function comprehensive scores were obtained through factor analysis. Then a rat model of chronic AlCl₃ exposure was established. The detection method of Al levels and protein expression were the same as mentioned-above.

RESULTS

Compared with the Q1 group, the DST, VFT, and comprehensive cognitive function scores of the Q4 group were lower(P < 0.05). For every 1μg/L increase in plasma Al concentration, the risk of cognitive impairment increases 1.051 times (95 %CI:1.031,1.072). Both NMDAR1 and NMDAR2A protein expression level of Q1 group were higher than those of Q2, Q3, Q4 group (all P < 0.05). The mediating effect ratio of NMDAR1 between plasma Al levels and cognitive function comprehensive scores was a1*b1/c=11.30 %, and the mediating effect ratio of NMDAR2A was |a2*b2/c|=21.77 %. Compared with control group, the escape latency of rats in the high Al dose group was longer day by day (P < 0.05). With the increase of Al dose, the relative expression of NMDAR1, NMDAR2A, NMDAR2B, GluR1 and mGluR5 in cerebral cortex and lymphocytes of rats were decreased (P < 0.05). The result of correlation analysis on NMDAR1 protein expression between brain cortex and lymphocyte showed that the correlation coefficient is r = 0.646(P < 0.05).

CONCLUSION

Taking together the results from both Al exposed workers and animal, there is a certain correlation between NMDAR1 protein contents of brain cortex and peripheral lymphocytes. We propose that lymphocyte NMDAR1 could be considered as a peripheral potential marker of cognitive impairment for further observation.

Relationship between the expression of TNFR1-RIP1/RIP3 in peripheral blood and cognitive function in occupational Al-exposed workers: A mediation effect study

Aluminium (Al), not essential for biological activities, accumulates in the tissues. It exerts toxic effects on the nervous system, inducing in humans' irreversible cognitive impairment. In this study, a cluster sampling method was used to observe the cognitive function of long-term occupational Al-exposed workers in a large Al factory, and determine the expression of peripheral blood tumour necrosis factor receptor 1 (TNFR1), receptor-interacting protein 1 (RIP1), and RIP3. TNF-alpha, expressed in blood macrophages and microglia, with its receptors TNFR1, TR1 and TR3, enhances the necroptosis of neurons. Additionally, the relationship between the expression of TNFR1, RIP1, and RIP3 in the peripheral blood of long-term occupational Al-exposed workers and changes in their cognitive function was explored. The differences in the distributions of clock drawing test (CDT) scores among the three groups were statistically significant (P < 0.05). The results of correlation analysis showed that RIP1 and RIP3 protein contents were negatively correlated with mini-mental state examination (MMSE) and CDT scores (P < 0.05). Plasma Al content was positively correlated with other biological indicators (P < 0.05), and negatively correlated with MMSE and CDT scores (P < 0.05). Results showed that RIP3 protein had an incomplete mediation effect between plasma Al content and cognitive function. This suggests that Al may affect cognitive function by influencing the expression of TNFR1, RIP1, and RIP3 in the nervous system.

Longitudinal study of the effects of occupational aluminium exposure on workers' cognition

OBJECTIVE

To explore the effects of occupational aluminium(Al) exposure on workers' cognition through a longitudinal study.

METHODS

The study population consisted of 276 workers in an Al factory. In 2014, we used inductively coupled plasma mass spectrometry (ICP-MS) to determine the plasma aluminium (P-Al) concentration of the workers, and a combined questionnaire to test the workers' cognitive function. Followed-up in 2016, the workers were tested again for cognitive function. Generalized linear regression was used to assess the association between P-Al concentration and cognitive scores, and multivariable logistic regression was used to assess the risk of cognitive decline caused by Al exposure.

RESULTS

Generalized linear regression results showed that a non-significant association was found between the P-Al concentration and cognitive test scores (P > 0.05) in 2014. Two years later, each 10-fold increase in P-Al concentration was inversely associated with the score of Mini-Mental state examination (MMSE) (β: -0.53, 95% CI: -0.86, -0.20) and Fuld object memory evaluation (FOME) (β: -0.93, 95% CI: -1.62, -0.24). Each 10-fold increase in P-Al concentration was inversely associated with MMSE_2016-2014 (β: -0.38, 95% CI: -0.74, -0.01) and FOME_2016-2014 (β: -1.20, 95% CI: -1.95, -0.45). There was a statistically significant difference in the average annual rate of change of MMSE and FOME with the tertile of P-Al concentration increase (P < 0.05). The multivariable logistic regression results showed that as the P-Al concentration increased, the risk of a FOME score decline increased (P_trend = 0.009).

CONCLUSIONS

Continuous occupational Al exposure can damage workers' overall cognitive ability, especially episodic memory function.

Increased aluminum and lithium and decreased zinc levels in plasma is related to cognitive impairment in workers at an aluminum factory in China: A cross-sectional study

BACKGROUND

Previous studies have shown that multiple imbalances of metal ions in the brain are closely associated with the neurodegenerative disorders. Our studies have shown that long-term working exposure to aluminum induces increased plasma aluminum levels and causes cognitive impairment in workers at aluminum factories.

OBJECTIVE

To explore the levels of nine metals in plasma and the effect on cognitive function among in-service workers.

METHODS

In this cross-sectional study, cognitive function was assessed using the Montreal Cognitive Assessment (MoCA), which included seven subitems: executive/visuospatial abilities; naming; attention and calculation; language; abstract; recall; and orientation. The plasma levels of nine kinds of metals were measured by inductively coupled plasma-mass spectrometry (ICP-MS). A multivariate generalized linear regression model and Bayesian kernel machine regression (BKMR) were selected to estimate the relationship between metal plasma level and MoCA scores with adjustment for confounders.

RESULTS

One hundred and eighty-seven workers participated in this study. In the multivariable generalized linear model, among these nine metals studied, five were related to the MoCA score: aluminum, lithium, cobalt, zinc and chromium. In the BKMR model, a significantly negative correlation between the plasma aluminum, lithium and the total MoCA score was observed. Moreover, for subitems on the MoCA scale, the plasma levels of lithium, aluminum, and zinc had a significant correlation with the executive/visuospatial abilities, naming, and orientation abilities, respectively. The log-transformation concentrations of plasma aluminum and lithium were negatively correlated with the executive/visuospatial abilities and naming abilities, respectively. The log-transformation plasma zinc concentration was positively correlated with orientation abilities.

CONCLUSION

Based on the results, we determined that increased aluminum and lithium and decreased zinc levels in plasma were associated with the incidence of mild cognitive impairment (MCI) in workers at a Chinese aluminum plant.

Cross-sectional study based on occupational aluminium exposure population

To evaluate the different characteristics of cognitive impairment caused by occupational aluminium exposure at different ages, we surveyed 1660 workers in Shanxi Aluminium Plant, China, and assessed their cognitive function and plasma aluminium concentration. In multiple linear regression, the scores of the digit-span test (DST) and digit-span backward test (DSBT) were negatively correlated with plasma aluminium concentration when concentration reached 34.52 μg/L in younger group (＜40 years), while in the middle-aged group (≥40 years) only found when concentration reached 42.25 μg/L (β<0, P < 0.05). In logistic regression, when plasma aluminum concentration reached 42.25μg/L, odds ratios (95 % confidence interval) were 1.695 (1.062-2.705) and 3.270 (1.615-6.620) for DST, 7.644 (3.846-15.192) and 15.308 (4.180-56.059) for DSBT in middle-aged group and younger group, respectively. These results showed that aluminium exposures were associated with cognitive impairment among aluminium-exposed workers, particularly for young workers who were more susceptible.