Article

Elevated manganese and cognitive performance in school-aged children and their mothers.

Laboratory of Toxicology, College of Pharmacy, Federal University of Bahia, Brazil.
Environmental Research (Impact Factor: 3.24). 10/2010; 111(1):156-63. DOI: 10.1016/j.envres.2010.09.006
Source: PubMed

ABSTRACT Growing evidence suggests that excess manganese (Mn) in children is associated with neurobehavioral impairments. In Brazil, elevated hair Mn concentrations were reported in children living near a ferro-manganese alloy plant.
We investigated these children's and caregivers' cognitive function in relation to bioindicators of Mn exposure.
In this cross-sectional study, the WISC-III was administered to 83 children aged between 6 and 12 years; the Raven Progressive Matrix was administered to the primary caregivers (94% mothers), who likewise responded to a questionnaire on socio demographics and birth history. Mn in hair (MnH) and blood (MnB) and blood lead (PbB) were measured by graphite furnace atomic absorption spectrometry (GFAAS).
Children's mean MnB and MnH were 8.2 μg/L (2.7-23.4) and 5.83 μg/g (0.1-86.68), respectively. Mean maternal MnH was 3.50 μg/g (0.10-77.45) and correlated to children's MnH (rho=0.294, p=0.010). Children's MnH was negatively related to Full-Scale Intelligence Quotient (IQ) and Verbal IQ; β coefficients for MnH were -5.78 (95% CI -10.71 to -0.21) and -6.72 (-11.81 to -0.63), adjusted for maternal education and nutritional status. Maternal MnH was negatively associated with performance on the Raven's (β=-2.69, 95% CI -5.43 to 0.05), adjusted for education years, family income and age.
These findings confirm that high MnH in children is associated with poorer cognitive performance, especially in the verbal domain. Primary caregiver's IQ is likewise associated to Mn exposure, suggesting that, in this situation, children's cognition may be affected directly and indirectly by Mn exposure.

1 Bookmark
 · 
107 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Exposure to airborne manganese (Mn) has been associated with neurotoxic effects, including motor and cognitive deficits. The main deficits related to excessive exposure to Mn are predominantly the dysfunction of fronto-striatal and dopaminergic circuits observed in animal experimental studies, which are involved in attention, working memory and motor function. The present study aims to assess the association between elevated Mn exposure and performance on executive function and attention neuropsychological tests in children living in two communities near a ferro-manganese alloy plant. Seventy children aged between 7 and 12 years with no history of neurologic disease and an estimated IQ >68 (Vocabulary and Block Design subtests) that had lived near the iron-Mn production alloy plant for at least 1.5 years were included. Participants were assessed for cognitive functioning with neuropsychological measures for sustained attention (Test of Visual Attention - TAVIS-3R), cognitive flexibility (WCST), and verbal and visual working memory (WISC-III Digit Span subtest and Corsi Block). Manganese hair (MnH) levels were used as a biomarker of exposure. Mean scores among study participants were lower than general population norms/averages for Block Design, Digit Span, Reaction Time and Commission Errors. The median MnH level was 11.48 (range 0.52 - 55.74) μg/g, and no difference between sexes was observed. Spearman's correlation analysis showed a significant inverse correlation between MnH levels and estimated IQ (rho= -0.448, p=0.0001), Vocabulary (rho= -0.272, p=0.02), Block Design (rho= -0.485, p=0.00002) and Digit Span (rho= -0.410, p=0.0004). Multiple regression analyses detected inverse associations between log MnH and scores on estimated IQ (β=-9.67; 95%CI=-16.97 to -2.37), Block Design (β=-2.50; 95%CI=-3.91 to -1.10) and Digit Span Total (β=-2.59; 95%CI=-4.13 to -1.05) standardized scores and the number of correct answers in forward and backward Digit Span methods, after adjusting for covariates (β -1.32=95%CI=-2.23 to -0.40; β=-1.09 95%CI=-2.02 to -0.16, respectively). The results suggest that airborne Mn exposure may be associated with lower IQ and neuropsychological performance in tests of executive function of inhibition responses, strategic visual formation and verbal working memory. Executive function is dependent on the fronto-striatal circuit, which may be disrupted by Mn accumulation in the brain.
    NeuroToxicology 12/2013; · 3.05 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High levels of waterborne manganese have been associated with problematic behavior in school-aged children, however to date this has not been reported for children exposed to airborne manganese. The objective of the present study was to examine behavioral traits among children with exposure to airborne manganese from a ferro-manganese alloy plant, located in the metropolitan region of Salvador, Brazil. The study included 34 boys and 36 girls, aged 7 to 12 years, living in two communities within a 3-km radius from the plant. For each child, hair manganese levels (MnH) and blood lead (PbB) levels were analyzed by graphite furnace atomic absorption spectrometry. The Children's Behavior Check List (CBCL) (Portuguese version validated in Brazil) was administered to parents or caregivers, providing scale scores of internalizing (withdrawn, somatic complaints, and anxious/depressed scales), externalizing (disruptive and aggressive) behaviors and a separate scale for attention problems. Median and range for MnH and PbB were 11.48μg/g (range: 0.52 - 55.74); 1.1μg/dL (range: 0.5 - 6.1), respectively. Spearman correlation analyses showed that several behavioral indices were significantly correlated with MnH levels for girls, but not for boys: Total externalizing behavior (rho=0.484 vs rho=0.041) and attention problem scores (rho=0.542 vs rho=0.003) coefficients were significantly at p<0.001 level, respectively for girls and boys. No significant correlation was observed with any of the internalizing sub-scales. A linear regression model was fitted with the Total Externalizing behavior, Inattention and Total CBCL scores as dependent variables, with log transformed MnH stratified by sex, adjusting for age and maternal IQ. Total externalizing behaviors and attention problem scores were significantly associated with girls' MnH levels but not with boys'. Adjusting for maternal IQ, the β-coefficients for LogMnH associations with total externalizing and attention problems are 8.85 (95%CI 2.44 to 15.24) and 4.03 (95%CI 1.50 to 6.56) for girls. For boys, after adjusting for age, the β-coefficients are 0.08 (95%CI -11.51 to 11.66) and -0.05 (95%CI -4.34 to 4.25), respectively. The findings of this study suggest a positive association between elevated Mn exposure and externalizing behavioral problems and inattention, with girls presenting more pronounced effects. Future studies on Mn exposure in children should attempt to further elucidate sex and/or gender differences in Mn exposed populations.
    NeuroToxicology 10/2013; · 3.05 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The current study was designed to evaluate the sensitivity, feasibility, and effectiveness of the pallidal index (PI) serving as a biomarker of brain manganese (Mn) accumulation, which would be used as an early diagnosis criteria for Mn neurotoxicity. The weighted mean difference (WMD) of the PI between control and Mn-exposed groups was estimated by using a random-effects or fixed-effects meta-analysis with 95% confidence interval (CI) performed by STATA software version 12.1. Moreover, the R package "metacor" was used to estimate correlation coefficients between PI and blood Mn (MnB). A total of eight studies with 281 occupationally Mn-exposed workers met the inclusion criteria. Results were pooled and performed with the Meta-analysis. Our data indicated that the PI of the exposed group was significantly higher than that of the control (WMD: 7.76; 95% CI: 4.86, 10.65; I2 = 85.7%, p<0.0001). A random effects model was used to perform meta-analysis. These findings were remarkably robust in the sensitivity analysis, and publication bias was shown in the included studies. Seven out of the eight studies reported the Pearson correlation (r) values. Significantly positive correlation between PI and MnB was observed (r = 0.42; 95% CI, 0.31, 0.52). PI can be considered as a sensitive, feasible, effective and semi-quantitative index in evaluating brain Mn accumulation. MnB can also augment the evaluation of brain Mn accumulation levels in the near future. However, the results should be interpreted with caution.
    PLoS ONE 04/2014; 9(4):e93900. · 3.53 Impact Factor

Full-text (2 Sources)

Download
40 Downloads
Available from
May 22, 2014