Aboud Frances E, Bougma Karim, Lemma Tizita, Marquis Grace S
Department of Psychology, McGill University, Montreal, Québec, Canada.
School of Dietetics and Human Nutrition, McGill University, Sainte Anne-de-Bellevue, Québec, Canada.
Matern Child Nutr. 2017 Apr;13(2). doi: 10.1111/mcn.12322. Epub 2016 May 3.
A cluster randomized effectiveness trial was used to examine the effects on mental development of introducing iodized salt to children 4 to 6 years of age in Ethiopia, where there were reportedly high levels of iodine deficiency. Sixty district clusters were randomized to receive iodized salt early at their markets with assistance from regular salt distributors or later as introduced by market forces. At pre- and post-iodization, 1602 children were given cognitive/language tests (namely School Readiness, WPPSI verbal reasoning, WPPSI Matrix reasoning), and mothers were interviewed concerning demographics, nutrition and health. Children's weight, height, urine and a blood sample were taken. Analyses of covariance, adjusting for clustering and baseline levels were conducted. Urinary iodine concentrations were significantly higher at endline in the intervention children than controls though both medians were above threshold. Overall, less than 5% were anemic. There were no significant main effect differences between groups on the cognitive/language tests, but there were effect modifiers, namely mother's education, child's sex and diet. For example, the intervention group performed better on the school readiness test than controls if their mothers had attended school, but not otherwise. In conclusion, the data are consistent with negative findings from studies where children 6 to 12 years were supplemented with an iodine capsule, indicating that the benefits of iodine, in salt or capsule form, for brain development may be restricted to children under 3 years. Yet, benefits may be tied to those with more educational resources or may compensate for conditions of disadvantage.
一项整群随机效应试验被用于研究在埃塞俄比亚对4至6岁儿童引入碘盐对其智力发育的影响，据报道该国碘缺乏水平较高。60个地区整群被随机分为两组，一组在正规食盐经销商的协助下在其市场较早引入碘盐，另一组则由市场力量较晚引入。在碘盐引入前后，对1602名儿童进行了认知/语言测试（即入学准备测试、韦氏幼儿智力量表言语推理测试、韦氏幼儿智力量表矩阵推理测试），并就人口统计学、营养和健康状况对母亲进行了访谈。采集了儿童的体重、身高、尿液和血样。进行了协方差分析，并对聚类和基线水平进行了调整。干预组儿童在研究结束时的尿碘浓度显著高于对照组，尽管两组中位数均高于阈值。总体而言，贫血率低于5%。两组在认知/语言测试上没有显著的主效应差异，但存在效应修饰因素，即母亲的教育程度、孩子的性别和饮食。例如，如果母亲上过学，干预组在入学准备测试中的表现优于对照组，否则则不然。总之，这些数据与对6至12岁儿童补充碘胶囊的研究的负面结果一致，表明碘盐或碘胶囊形式的碘对大脑发育的益处可能仅限于3岁以下儿童。然而，益处可能与拥有更多教育资源的人相关，或者可能弥补不利条件。
