Abstract
- Background
The effects of severe iodine deficiency during critical periods of brain development are well documented; however, little is known about the consequences of milder forms of iodine deficiency on neurodevelopment. The objective of this study was to determine whether supplementing mildly iodine-deficient children with iodine improves cognition.
- Methods
A randomized, double-blind, placebo-controlled trial was conducted in 184 children aged 10–13 years in Dunedin, New Zealand ($\text{ACTRN12608000222347}$). Children were randomly assigned to receive a daily tablet containing either $150\text{ }\mu\text{g}$ of iodine or placebo for 28 weeks. Biochemical, anthropometric, and dietary data were collected at baseline and after 28 weeks. Cognitive performance was assessed using four subtests from the Wechsler Intelligence Scale for Children ($\text{WISC}$).
- Results
At baseline, children were mildly iodine deficient, with a median urinary iodine concentration ($\text{UIC}$) of $63\text{ }\mu\text{g/L}$ and a thyroglobulin concentration of $16.4\text{ }\mu\text{g/L}$. After 28 weeks, iodine status significantly improved in the supplemented group ($\text{UIC}$: $145\text{ }\mu\text{g/L}$; thyroglobulin: $8.5\text{ }\mu\text{g/L}$), whereas the placebo group remained deficient ($\text{UIC}$: $81\text{ }\mu\text{g/L}$; thyroglobulin: $11.6\text{ }\mu\text{g/L}$). Iodine supplementation significantly improved scores for two cognitive subtests: picture concepts ($p = 0.023$) and matrix reasoning ($p = 0.040$). No significant differences were observed for letter-number sequencing ($p = 0.480$) or symbol search ($p = 0.608$). Overall, the cognitive score of the iodine-supplemented group was $0.19\text{ }SD\text{s}$ higher than that of the placebo group ($p = 0.011$).
- Conclusions
Iodine supplementation improved perceptual reasoning in mildly iodine-deficient children. These findings suggest that mild iodine deficiency could prevent children from attaining their full intellectual potential.
https://www.sciencedirect.com/science/article/pii/S0002916523266381