Median Urinary Iodine Concentration in School-Age Children Does Not Consistently Vary by Inflammation or Sociodemographic Factors: Multi-Country Analysis From BRINDA

Abstract Objectives Iodine is an essential micronutrient that plays a critical role in child growth and development. This study aimed to examine median urinary iodine concentrations (mUIC) by country and key health and sociodemographic factors. Methods Nationally representative surveys from Bangladesh (n = 1282), Ecuador (n = 6063), Malawi (n = 758), and the U.S. (n = 3548) were analyzed to estimate mUIC among school-age children (6–12 years old) from the Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project. WHO classifies mUICs into four categories: insufficient iodine intake, defined as mUIC < 100 μg/L; adequate iodine nutrition categorized as mUIC from 100 to 199 μg/L; above the required intake as mUIC from 200 to 299 μg/L; and excessive intake as mUIC >300 μg/L. Inflammation was defined by Alpha 1-acid glycoprotein (AGP) of >1 g/L or C-reactive protein (CRP) of >5 mg/L. Underweight was defined by Body Mass Index (BMI) for age z-score < −2 and overweight was defined as BMI z-score >2. Complex survey designs were applied to calculate the mUIC for each country. Design-based median tests were used to examine whether mUICs differed by age, sex, weight status, and inflammation status by country. Results mUIC was adequate in Bangladesh (138.5 μg/L) and above the required intake in Ecuador (251.0 μg/L), Malawi (265.5 μg/L), and the U.S. (230.0 μg/L). Boys had a significantly higher mUIC than girls in Ecuador (257.0 vs. 237.0 μg/L, P = 0.03), Malawi (302.0 vs. 226.8 μg/L, P = 0.01), and the U.S. (264.0 vs. 210.3 μg/L, P = 0.04). mUIC was not significantly different by age groups (6–9 vs. 10–12 years), weight status, and inflammation status, except in Bangladesh where the group with inflammation had a higher mUIC than the group without (153.0 vs. 130.0 μg/L, P = 0.04). Conclusions Although heterogeneity existed in mUICs across different countries, iodine intake was adequate or above requirements in all four countries. Compared to girls, boys had higher mUIC in 3 countries, and the group with inflammation had higher mUIC in 1 country. mUIC did not differ by other socioeconomic or anthropometric factors. Funding Sources Bill & Melinda Gates Foundation, Centers for Disease Control and Prevention, Eunice Kennedy Shriver National Institute of Child Health and Human Development, HarvestPlus, and the United States Agency for International Development.