The Effects of Iodized Salt on Cognitive Development in Ethiopia
The Effects of Iodized Salt on Cognitive Development in Ethiopia
Many school children in Ethiopia and their mothers are known to be iodine deficient.
 Prevalence in the Amhara region is around 29%. Micronutrient Initiative, a development
 organization based in Ottawa, plans to help iodize the salt by providing iodization machines
 and iodine to the salt producers in Lake Afdira where salt is produced and distributed to the
 population of Ethiopia. Although it is generally assumed that iodine is important for
 cognitive development, very few studies examining the effects of iodized salt have been
 conducted. Studies using a single dose of iodine capsules with children 6 to 12 years showed
 mixed outcomes with approximately 25% yielding positive outcomes for the intervention
 children. Sixty districts in Amhara will be randomly selected and randomly assigned so that
 half receive early delivery of iodized salt. Approximately 6200 mothers and their children
 6-, 18-, or 60-months old will be recruited from 1-2 villages in each of the 60 districts,
 with the help of government-paid Health Extension Workers, for a 12-mo longitudinal study
 starting in May 2011, prior to the introduction of iodized salt. These same mothers and
 children will be visited 12 months later for repeated measures. Measures include nutritional
 status such as height and hemoglobin, along with iodine sufficiency (e.g., goitre, urinary
 iodine, thyroglobulin), and child development (Bayley Scales of Infant and Toddler
 Development III, Wechsler Preschool and Primary School Intelligence test for older children).
 Comparisons will be made within and between groups to determine whether iodized salt has an
 effect on children's mental development.
MATERIALS AND METHODS Sample size was estimated on the basis of the Bayley Scales of Infant
 and Toddler Development III (Bayley) where the mean is 100 and the standard deviation is 15.
 Using an effect size of 0.20 standard deviation, a beta of .05 and power of .80, and
 accommodating for clustering within villages and attrition, the investigators require a
 sample size of 800 for each group (intervention and control). Severely anemic children (< 8
 mg/L) will be referred for treatment and not included in the study.

 In this longitudinal study the investigators will recruit 3200 6-mo old infants and 1600
 children from each of two other age groups: 18-, and 60-months (inclusion criteria) and their
 mothers. The exclusion criteria: severe anemia (hemoglobin < 8g/dL). If children are too
 disabled to take a cognitive test, this will be noted but no cognitive testing administered.

 From six zones around Bahir Dar, the investigators will randomly select 60 districts. Half
 will be assigned randomly to start receiving iodized salt in July 2011; the other half will
 receive iodized salt as it becomes available in the market. From each district, 1-2 villages
 will be randomly selected for recruiting 30 children from each age group. It is assumed that
 with a pregnancy rate of 3.7%, approximately 166 children are born every year in a village of
 4500, and 13 are born every month. So within 3 months, starting in May 2011, 30 children of
 each age could be recruited.

 With the help of Health Extension Workers, trained field workers will identify the
 participants : children of eligible age. Mothers will provide written consent for themselves
 and their children to participate.

 Mothers will be interviewed at baseline and endline concerning the family's economic and
 demographic information, child's health and diet, and opportunities for stimulation of
 children (Home Observation for Measurement of the Environment Inventory; Center for
 Epidemiologic Studies Depression Scale symptom scores). Children's nutritional status will be
 measured with a food frequency questionnaire, length/height, weight, blood indicators for
 thyroid function (thyroglobulin, thyroxin, triiodothyronine) and iron status (hemoglobin,
 ferritin, soluble transferrin receptor), and inflammation (C-reactive protein), goiter, and
 urinary iodine. A maximum of 10 mL will be collected for blood by venipuncture. Finally,
 trained assistants will administer the Bayley Scales of Infant and Toddler Development III
 (cognitive, language, and fine motor scales) to children under-3 years and two Wechsler
 Preschool and Primary School Intelligence test subscales and School Readiness test for
 60-month olds. Salt will be collected at various places of purchase and in households to test
 for iodine content (first qualitatively, then quantitatively if iodized) at baseline and at
 the end of the study. All data collection will be done at home or a convenient site in the
 village.

 Conversion of diet into iodine content will be done based on food composition table.
 Anthropometric data will be converted to standardized scores using the new World Health
 Organization reference curves, using World Health Organization's software Anthro v. 2 for
 children up to 60 months of age.

 Analyses will compare the nutritional and developmental outcomes of two groups who differ in
 iodized salt exposure, covarying confounders such as mother's education, family assets,
 child's sex, and adjusting for clustering. Developmental scores will be derived for the
 Bayley subtests, and the Wechsler Preschool and Primary School Intelligence test. These tests
 typically assign 1 point for every correct answer and 0 points for incorrect answers; the
 summed continuous scores are then used for analysis. Potential confounds include the Home
 Observation for Measurement of the Environment Inventory and Center for Epidemiologic Studies
 Depression Scale symptom scores, which also are calculated as the sum of individual item
 points. Laboratory analyses will be conducted to determine hemoglobin, ferritin, soluble
 transferrin receptor, thyroglobulin, thyroxin, and triiodothyronine from blood samples, and
 iodine excretion from urine samples. Analyses of salt will also indicate whether salt
 consumed by participants in the intervention districts has the required ppm of iodine and
 more than salt consumed in control districts. If households in the control sites have higher
 than expected levels of iodine, this will be recorded and included in the analyses.
Inclusion Criteria:

 -  children within 15 days of 6, 18, and 60 months

 Exclusion Criteria:

 -  severe cognitive impairment so child cannot respond to Bayley Scales of Infant and
 Toddler Development III test