Iodine and Other Nutritional Predictors of Preschool-Aged Children's Development in Amhara, Ethiopia

Abstract

Objectives: The study examined nutritional and other predictors of mental development of preschool-aged children in northern Ethiopia. The current analysis of older children from the iodized salt project (see Infant study) included the effects of iodized salt, along with other determinants. Methods:  Using a cluster randomized design, 1550 children in 60 villages in Amhara, Ethiopia were given tests of School Readiness and Wechsler verbal and nonverbal reasoning, twice at 54-60 months and again at 69-78 months. Between these assessments, iodized salt was distributed early in the markets of 30 randomly assigned villages (intervention group) before it became available in 30 control villages. Results: The two groups were largely comparable at baseline. In addition to the effects of iodized salt on School Readiness (p=0.01) and nonverbal reasoning (p<0.10) seen at the endline, the following predictors were positively and significantly associated with cognitive outcomes:  height-for-age z-score (HAZ; p<0.0001), weight-for-age z-score (p<0.0001), family assets (p<0.0001), recent deworming (p=0.01), improved water/sanitation (p<0.01), and mother's education (p<0.05).  Although over two-thirds had palpable goiter, hemoglobin status was good (M=134 g/L).  Children overall performed relatively better on the School Readiness test (M=6.66 Intervention and 6.25 Control) than nonverbal reasoning (M= 4.15 Intervention and 3.95 Control)(theoretic ranges 0-19).  A multiple regression, following the Baron and Kenny mediation analysis, on School Readiness scores revealed that the intervention effect was partially mediated by HAZ (std β= 0.37 , p<0.0001).  Conclusions: In conclusion, iodized salt improved children's School Readiness skills and nonverbal reasoning, both directly, and indirectly by way of its effect on growth.