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Iodine and Mental Development of Children 5 Years Old and Under: A Systematic Review and Meta-Analysis
School of Dietetics and Human Nutrition, McGill University, 21111 Lakeshore Road, CINE Building, Sainte Anne-de-Bellevue, QC, H9X 3V9, Canada
Department of Psychology, McGill University, 1205 Dr. Penfield Avenue, Montreal, QC, H3A 1B1, Canada
Micronutrient Initiative, 180 Elgin Street, Suite 1000, Ottawa, ON, K2P 2K3, Canada
* Author to whom correspondence should be addressed.
Received: 10 December 2012; in revised form: 14 February 2013 / Accepted: 22 March 2013 / Published: 22 April 2013
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.
Keywords: children; iodine; mental development; systematic review; meta-analysis
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Bougma, K.; Aboud, F.E.; Harding, K.B.; Marquis, G.S. Iodine and Mental Development of Children 5 Years Old and Under: A Systematic Review and Meta-Analysis. Nutrients 2013, 5, 1384-1416.
Bougma K, Aboud FE, Harding KB, Marquis GS. Iodine and Mental Development of Children 5 Years Old and Under: A Systematic Review and Meta-Analysis. Nutrients. 2013; 5(4):1384-1416.
Bougma, Karim; Aboud, Frances E.; Harding, Kimberly B.; Marquis, Grace S. 2013. "Iodine and Mental Development of Children 5 Years Old and Under: A Systematic Review and Meta-Analysis." Nutrients 5, no. 4: 1384-1416.