Iodine and Mental Development of Children 5 Years Old and Under: A Systematic Review and Meta-Analysis

Abstract

Several reviews and meta-analyses have examined the effects of iodine on mental development. None focused on young children, so they were incomplete in summarizing the effects on this important age group. The current systematic review therefore examined the relationship between iodine and mental development of children 5 years old and under. A systematic review of articles using Medline (1980–November 2011) was carried out. We organized studies according to four designs: (1) randomized controlled trial with iodine supplementation of mothers; (2) non-randomized trial with iodine supplementation of mothers and/or infants; (3) prospective cohort study stratified by pregnant women’s iodine status; (4) prospective cohort study stratified by newborn iodine status. Average effect sizes for these four designs were 0.68 (2 RCT studies), 0.46 (8 non-RCT studies), 0.52 (9 cohort stratified by mothers’ iodine status), and 0.54 (4 cohort stratified by infants’ iodine status). This translates into 6.9 to 10.2 IQ points lower in iodine deficient children compared with iodine replete children. Thus, regardless of study design, iodine deficiency had a substantial impact on mental development. Methodological concerns included weak study designs, the omission of important confounders, small sample sizes, the lack of cluster analyses, and the lack of separate analyses of verbal and non-verbal subtests. Quantifying more precisely the contribution of iodine deficiency to delayed mental development in young children requires more well-designed randomized controlled trials, including ones on the role of iodized salt.

The relationship between unhealthy snacking at school and academic outcomes: a population study in Chilean schoolchildren

“…Most research studies performed in developing and middleincome countries have examined the association between macro-and micronutrient deficiencies and several measures of cognitive functioning in children (1)(2)(3) . The economic boom of the past two decades, however, has paved the way for an increase in non-communicable diseases associated with overweight and obesity since infancy.…”

Iodine deficiency: current status

“…В метаанализе исследований, изучавших влия-ние йода на умственное развитие детей до 5 лет, было выявлено, что уровень коэффициента интеллекта (IQ) у детей дошкольного возраста, не получавших йодопрофилактики, на 6,9-10,2 балла ниже, чем у детей с компенсированным дефицитом йода [40].…”

Iodine Deficiency in Latvia: Current Status and Need for National Recommendations

“…A meta-analysis published in 2013 revealed that at age 5, children lost 7.4 IQ points due to iodine deficiency during pregnancy (Bougma et al, 2013). Econometric models have established that this result not only is significant at the individual level but also affects society as a whole: a one-point decrease in IQ has been associated with a persistent 0.11% annual decrease in per capita gross domestic product (GDP).…”