Association between household unavailability of iodized salt and child growth: evidence from 89 demographic and health surveys.
Although a strong biological basis exists for a role of iodine in somatic growth failure in childhood, this relation has not been previously studied on a large scale to our knowledge.



We investigated if a general association exists between the household unavailability of iodized salt and child growth across countries.



We used 89 nationally representative, repeated, cross-sectional and mutually comparable demographic and health surveys that were conducted between 1994 and 2012 across 46 low- and middle-income countries. We analyzed the data for the outcome variables of stunting (low height-for-age), underweight (low weight-for-age), wasting (low weight-for-height), and low birth weight in children aged between 0 and 59 mo at the time of the interview with the use of logistic regression models. Our samples consisted of 390,328 children for the stunting analysis, 397,080 children for the underweight analysis, 384,163 children for the wasting analysis, and 187,744 children for the low-birth-weight analysis. Models were adjusted for individual, maternal, and household covariates and fixed effects on the level of the primary sampling unit.



In the fully adjusted models, the unavailability of iodized salt was associated with 3% higher odds of being stunted (95% CI of ORs: 1.00, 1.06; P = 0.04), 5% higher odds of being underweight (95% CI: 1.02, 1.09; P < 0.01), and 9% higher odds of low birth weight (95% CI: 1.02, 1.17; P = 0.01). When India was excluded from the sample, the association was only statistically significant (P = 0.05) for low birth weight.



Although we did not establish causality in our analysis, the findings might indicate that the causal effect of iodized salt on child growth, if it exists, is most profound in utero and is not universally effective across all countries with respect to longer-run child-growth outcomes such as stunting and underweight.
Department of Economics and Centre for Modern Indian Studies, University of Göttingen, Göttingen, Germany.
Marion
M
Krämer
Nutrition Section, UNICEF, New York, NY; and Departments of Nutrition.
Roland
R
Kupka
Social and Behavioral Sciences, and.
S V
SV
Subramanian
Department of Economics and Centre for Modern Indian Studies, University of Göttingen, Göttingen, Germany; Global Health and Population, Harvard T.H. Chan School of Public Health, Boston, MA svollmer@uni-goettingen.de.
Sebastian
S
Vollmer
D001724:Birth Weight; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003906:Developing Countries; D005191:Family Characteristics; D005260:Female; D006128:Growth; D006130:Growth Disorders / Q000209:etiology*; D006306:Health Surveys; D006801:Humans; D007182:Income; D007223:Infant; D007231:Infant, Newborn; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency*; D016015:Logistic Models; D008297:Male; D009751:Nutritional Requirements; D009752:Nutritional Status; D016017:Odds Ratio; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage; D013851:Thinness / Q000209:etiology*; D019282:Wasting Syndrome / Q000209:etiology*
D017673:Sodium Chloride, Dietary; C034024:iodized salt; D007455:Iodine
childhood undernutrition; demographic and health surveys; iodine; iodine deficiency; iodized salt; low birth weight; low- and middle-income countries; micronutrient deficiency; salt fortification; undernutrition