Background

Manganese is commonly found in water but potential neurotoxic effects from exposure through drinking water are poorly understood. We previously reported a cross-sectional study showing that drinking water Mn concentration was associated with lower IQ in children aged 6 to 13 years.

Objective

For this follow-up study, we aimed to re-assess the relation between exposure to Mn from drinking water and IQ at adolescence. In addition, we aimed to examine whether changes in drinking water Mn concentration was associated with changes in IQ scores.

Methods

From the 380 children enrolled in the baseline study, 287 participated to this follow-up study conducted in average 4.4 years after. Mn concentration was measured in home tap water and children's hair. The relationships between these Mn exposure indicators and IQ scores (Weschsler Abbreviated Scale of Intelligence) at follow-up were assessed with linear regression analysis, adjusting for potential confounders. Intra-individual differences in IQ scores between the two examinations were compared for children whose Mn concentration in water remained stable between examinations, increased or decreased.

Results

The mean age at follow-up was 13.7 years (range, 10.5 to 18.0 years). Geometric mean of Mn concentration in water at follow-up was 14.5 μg/L. Higher Mn concentration in water measured at follow-up was associated with lower Performance IQ in girls (β for a 10-fold increase = −2.8, 95% confidence intervals [CI] −4.8 to −0.8) and higher Performance IQ in boys (β = 3.9, 95% CI 1.4 to 6.4). IQ scores were not significantly associated with Mn concentration in hair, although similar trends as for concentration in water were observed. For children whose Mn concentration in water increased between baseline and follow-up, Performance IQ scores decreased significantly (intra-individual difference, −2.4 points).

Conclusion

Higher levels of Mn in drinking water were associated with lower Performance IQ in girls, whereas the opposite was observed in boys. These findings suggest long-term exposure to Mn through drinking water is associated differently with cognition in boys and girls.

中文翻译：

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饮水接触儿童的水锰含量变化和智力功能纵向评估

背景

锰通常存在于水中，但人们对通过饮用水接触造成的潜在神经毒性作用知之甚少。我们先前报道的一项横断面研究显示，饮用水中锰的浓度与6至13岁儿童的智商较低有关。

客观的

在此后续研究中，我们旨在重新评估饮用水中锰暴露与青春期智商之间的关系。此外，我们旨在检查饮用水中锰浓度的变化是否与智商得分的变化相关。

方法

在参加基线研究的380名儿童中，有287名儿童参加了平均4.4年后进行的随访研究。测定家庭自来水和儿童头发中的锰浓度。通过线性回归分析评估这些锰暴露指标与IQ评分（Weschsler缩写智力量表）之间的关系，并调整潜在的混杂因素。比较了两次检查之间的个体智商得分的个体差异，比较了两次检查之间水中锰浓度保持稳定，升高或降低的儿童。

结果

随访的平均年龄为13.7岁（范围为10.5至18.0岁）。随访时水中锰浓度的几何平均值为14.5μg/ L。随访中测得的水中较高的Mn浓度与女孩的较低的表现智商（β升高10倍= -2.8，95％置信区间[CI] -4.8至-0.8）和男孩的较高的表现智商相关（ β= 3.9，95％CI为1.4至6.4）。智商得分与头发中的锰含量没有显着相关，尽管观察到与水中的锰含量相似的趋势。对于基线和随访之间水中锰浓度增加的儿童，表现智商得分显着下降（个体内部差异为-2.4分）。

结论

饮用水中锰含量较高与女孩的表现智商低有关，而男孩则相反。这些发现表明，通过饮用水长期暴露于锰与男孩和女孩的认知不同。