Improved iodine status is associated with improved mental performance of schoolchildren in Benin

Background: An adequate iodine supply in utero and shortly after birth is k nown to be crucial to an individual's physical and mental development. The question of whether iodine supplementation later in life can exert a favora ble influence on the mental performance of iodine-deficient populations was addressed in various studies, but with contradictory results. Objective: The aim of this study was to examine the effect of an improvemen t in iodine status on mental and psychomotor performance of schoolchildren (7-11 y) who were moderately to severely iodine deficient. Design: The study, which was originally planned as a double-blind, randomiz ed, placebo-controlled intervention, was carried out in an iodine-deficient population of schoolchildren (n = 196) in northern Benin. As the populatio n began to have access to iodized salt during the 1-y intervention period, the study population was split post hoc-on the basis of urinary iodine conc entrations-into a group with improved iodine status and a group with unchan ged iodine status. Changes in mental and psychomotor performance over the i ntervention period were compared. Results: Children with increased urinary iodine concentrations had a signif icantly greater increase in performance on the combination of mental tests than did the group with no change in urinary iodine concentrations. Conclusions: An improvement in iodine status, rather than iodine status its elf, determined mental performance in this population, which was initially iodine deficient. These findings suggest a "catch-up" effect in terms of me ntal performance.