Ot clearly report the procedure of randomizing women and selected post hoc for testing only the children of women supplemented prior to conception. Both studies were published before reporting guidelines became available, so a number of details such as concealment of allocation and intention-to-treat were not clearly stated. The effect sizes of this current review translate into a range of IQ points from 6.9 to 10.2 lost due to iodine deficiency, assuming that iodine treated or iodine sufficient groups attain closer to expected levels and others have “lost” IQ points. An earlier meta-analysis reported an effect size of 0.90 but this was based on observation studies of children and adults using a variety of designs and mental development measures [24]. The limitations of this meta-analysis have been mentioned earlier in this paper. The meta-analysis of studies in China used observational and non-randomized designs and the range of effect sizes was 0.58 to 0.83 depending on the design [26]. We believe that the best estimate to date of effect size in children 5 years old and under due to iodine deficiency in utero or early infancy is 0.49, which translates into 7.4 IQ points lost due to iodine deficiency. This estimate is based on the intervention studies, which despite some limitations had relatively rigorous designs and age-appropriate mental development tests. Caution should be used when interpreting the findings from this review. Our discussion of limitations will be grouped under the following points: VP 63843 manufacturer Confounders that arise in non-randomized designs; sample size and accommodation for Oroxylin A web clustering; iodine biomarkers; conceptualization of mental development; unmeasured side effects of maternal iodine status; and consideration of the use of iodized salt on mental development. Confounders in non-randomized and cluster randomized studies were rarely addressed. These include known correlates of mental development which might differ between intervention groups, such as family assets, family dietary diversity, mother’s education, and home stimulation, along with the weight, height and prematurity status of children [17]. Assigning villages to receive supplements alsoNutrients 2013,leaves open to question the potential differences among mothers in the two villages. Baseline differences in social and economic status would normally be measured and statistically controlled in the final analysis. There was no mention of such measurement or statistical control in the eight studies using non-randomized supplemented groups. Some differences in nutritional status were reported [46,58,60,61], suggesting that other unmeasured differences existed. Prospective cohort studies would be even more affected by confounds. Characteristics of the mother, such as her distance from the clinic and her years of schooling would influence children’s mental outcomes if supplementation depended on the timing of her arrival at the clinic [47,65]. Failure to include confounds in the statistical analysis may serve to inflate effect sizes. While we have addressed here only the issue of controlling for confounds within a study, there is the additional caveat concerning comparisons across studies where differences in socioeconomic status, access to health services, and nutritional status other than iodine may account for differences in mental development and may modify the effects of iodine supplementation on mental development. Sample sizes were generally small with the median.Ot clearly report the procedure of randomizing women and selected post hoc for testing only the children of women supplemented prior to conception. Both studies were published before reporting guidelines became available, so a number of details such as concealment of allocation and intention-to-treat were not clearly stated. The effect sizes of this current review translate into a range of IQ points from 6.9 to 10.2 lost due to iodine deficiency, assuming that iodine treated or iodine sufficient groups attain closer to expected levels and others have “lost” IQ points. An earlier meta-analysis reported an effect size of 0.90 but this was based on observation studies of children and adults using a variety of designs and mental development measures [24]. The limitations of this meta-analysis have been mentioned earlier in this paper. The meta-analysis of studies in China used observational and non-randomized designs and the range of effect sizes was 0.58 to 0.83 depending on the design [26]. We believe that the best estimate to date of effect size in children 5 years old and under due to iodine deficiency in utero or early infancy is 0.49, which translates into 7.4 IQ points lost due to iodine deficiency. This estimate is based on the intervention studies, which despite some limitations had relatively rigorous designs and age-appropriate mental development tests. Caution should be used when interpreting the findings from this review. Our discussion of limitations will be grouped under the following points: confounders that arise in non-randomized designs; sample size and accommodation for clustering; iodine biomarkers; conceptualization of mental development; unmeasured side effects of maternal iodine status; and consideration of the use of iodized salt on mental development. Confounders in non-randomized and cluster randomized studies were rarely addressed. These include known correlates of mental development which might differ between intervention groups, such as family assets, family dietary diversity, mother’s education, and home stimulation, along with the weight, height and prematurity status of children [17]. Assigning villages to receive supplements alsoNutrients 2013,leaves open to question the potential differences among mothers in the two villages. Baseline differences in social and economic status would normally be measured and statistically controlled in the final analysis. There was no mention of such measurement or statistical control in the eight studies using non-randomized supplemented groups. Some differences in nutritional status were reported [46,58,60,61], suggesting that other unmeasured differences existed. Prospective cohort studies would be even more affected by confounds. Characteristics of the mother, such as her distance from the clinic and her years of schooling would influence children’s mental outcomes if supplementation depended on the timing of her arrival at the clinic [47,65]. Failure to include confounds in the statistical analysis may serve to inflate effect sizes. While we have addressed here only the issue of controlling for confounds within a study, there is the additional caveat concerning comparisons across studies where differences in socioeconomic status, access to health services, and nutritional status other than iodine may account for differences in mental development and may modify the effects of iodine supplementation on mental development. Sample sizes were generally small with the median.
