Mild iodine deficiency during fetal/neonatal life and neuropsychological impairment in Tuscany

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Abstract
The neuropsychological performance of schoolchildren living in areas with present and past iodine deficiency in Tuscany was investigated. Children were submitted to: a) block design subtest of the Wechsler Intelligence Scale for Children-Revised (WISC-R) and a modified version of the WISC-R coding subtest which evaluate the general neuropsychological and cognitive performance, independently from familial cultural background; b) simple reaction time (RT) session which evaluates the efficiency of the whole information processing and nervous transmission mechanisms. Neuropsychological performance was tested in 107 children living in Borgo a Mozzano, an area of mild iodine deficiency (IDA) with a median urinary iodine excretion (UIE) of 64 μg/L (mean±SD: 80.1±57). One hundred and six sex and age-matched children living in Marina di Pisa, an iodine sufficient coastal village of Tuscany (ISA) with a median UIE of 142 μg/L (mean±SD: 173±95) were used as controls. Tests for neuropsychological performance were performed in 57 children living in the village of Vagli, an area with past iodine deficiency (PIDA): 30 children born before iodine prophylaxis (Group 1), when the median UIE was 32 μg/L (mean±SD: 47±22), 27 children born after the institution of iodine prophylaxis (Group 2), when the median UIE was 109 μg/L (mean±SD:130±73). Sex and age-matched ISA-children were used as controls for each group. RTs were significantly delayed (p<0.05) in IDA than in ISA children, while block design and coding subtests showed no significant difference. PI-DA children of Group 1, but not those of Group 2 showed significantly delayed RTs when compared to controls, block design and coding tests being unaffected. In conclusion, our data indicate that: i) mild iodine deficiency may impair the rate of motor response to perceptive stimuli, as assessed by measurement of reaction time, in the absence of general cognitive impairment; ii) the effects of exposure to iodine deficiency during fetal/neonatal life, in spite of correction in the early childhood, may persist longer. Our findings also suggest that the measurement of simple RTs is a sensitive test to detect subtle neurological damages in mild iodine deficiency.

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