Axelrad Daniel A, Bellinger David C, Ryan Louise M, Woodruff Tracey J
Office of Policy, Economics, and Innovation, U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue NW, Washington, DC 20460, USA.
Environ Health Perspect. 2007 Apr;115(4):609-15. doi: 10.1289/ehp.9303. Epub 2007 Jan 11.
Prenatal exposure to mercury has been associated with adverse childhood neurologic outcomes in epidemiologic studies. Dose-response information for this relationship is useful for estimating benefits of reduced mercury exposure.
We estimated a dose-response relationship between maternal mercury body burden and subsequent childhood decrements in intelligence quotient (IQ), using a Bayesian hierarchical model to integrate data from three epidemiologic studies.
Inputs to the model consist of dose-response coefficients from studies conducted in the Faroe Islands, New Zealand, and the Seychelles Islands. IQ coefficients were available from previous work for the latter two studies, and a coefficient for the Faroe Islands study was estimated from three IQ subtests. Other tests of cognition/achievement were included in the hierarchical model to obtain more accurate estimates of study-to-study and end point-to-end point variability.
We find a central estimate of -0.18 IQ points (95% confidence interval, -0.378 to -0.009) for each parts per million increase of maternal hair mercury, similar to the estimates for both the Faroe Islands and Seychelles studies, and lower in magnitude than the estimate for the New Zealand study. Sensitivity analyses produce similar results, with the IQ coefficient central estimate ranging from -0.13 to -0.25.
IQ is a useful end point for estimating neurodevelopmental effects, but may not fully represent cognitive deficits associated with mercury exposure, and does not represent deficits related to attention and motor skills. Nevertheless, the integrated IQ coefficient provides a more robust description of the dose-response relationship for prenatal mercury exposure and cognitive functioning than results of any single study.
在流行病学研究中，孕期接触汞已被证明与儿童期不良神经学后果有关。这种关系的剂量反应信息有助于评估减少汞接触的益处。
我们使用贝叶斯分层模型整合三项流行病学研究的数据，估计母亲汞负荷与随后儿童智商（IQ）下降之间的剂量反应关系。
该模型的输入数据包括在法罗群岛、新西兰和塞舌尔群岛进行的研究中的剂量反应系数。后两项研究的智商系数可从先前的工作中获得，法罗群岛研究的系数是根据三项智商子测试估计的。分层模型中还纳入了其他认知/成就测试，以更准确地估计不同研究之间以及不同终点之间的变异性。
我们发现，母亲头发汞含量每增加百万分之一，智商下降的中心估计值为-0.18个智商点（95%置信区间为-0.378至-0.009），这与法罗群岛和塞舌尔群岛的研究估计值相似，且幅度低于新西兰研究的估计值。敏感性分析得出了类似的结果，智商系数的中心估计值在-0.13至-0.25之间。
智商是评估神经发育影响的一个有用终点，但可能无法完全代表与汞接触相关的认知缺陷，也不能代表与注意力和运动技能相关的缺陷。尽管如此，综合智商系数比任何单一研究的结果更有力地描述了产前汞接触与认知功能之间的剂量反应关系。
