Children’s performance on Raven’s Coloured progressive matrices in Portugal: The Flynn effect

Association between Elevated Iodine Intake and IQ among School Children in Portugal

The goal of this work was to examine whether elevated iodine intake was associated with adverse effects on IQ among school-age children in Portugal. In a representative sample of children from the north of the country, IQ percentiles by age (assessed with Raven’s Colored Progressive Matrices) were dichotomized to <50 (“below-average” IQs) and ≥50. Morning urine iodine concentrations, corrected for creatinine, were dichotomized to <250 µg/g and ≥250 µg/g, according to the European Commission/Scientific Committee on Food’s tolerable upper level of daily iodine intake for young children. Data were examined with Chi-square tests, logistic regression, and GLM univariate analysis. The sample (N = 1965) was classified as generally iodine-adequate (median urinary iodine concentration = 129 µg/L; median iodine-to-creatinine ratio = 126 µg/g) according to the WHO’s criteria. A greater proportion of children in the ≥250 µg/g group had below-average IQs, compared to children with less than 250 µg/g (p = 0.037), despite a sizable (though non-significant) proportion of children in the less-than-250 µg/g group also presenting below-average IQs, at the bottom of the iodine distribution (<50 µg/g). The proportion of below-average IQs increased with increasingly elevated iodine concentrations (p = 0.047). The association remained significant after the adjustment for confounders, with the elevated iodine group showing increased odds of having below-average IQs when compared with the non-elevated iodine group (OR 1.55; 95% CI 1.11−2.17; p = 0.011). Consistently, the former group presented a lower mean IQ than the latter (p = 0.006). High iodine intake was associated with lower IQs even in a population classified as iodine-adequate. These results bear on child cognition and on initiatives involving iodine supplementation.

Comparison of WPPSI-IV and WISC-V cognitive profiles in 6-7-year-old Finland-Swedish children - findings from the FinSwed study

The Wechsler scales are among the most widely used tests in cognitive and neuropsychological assessments. When assessing children aged 6:0-7:7 years the clinician can choose between Wechsler Preschool and Primary Scale of Intelligence - Fourth Edition (WPPSI-IV) and Wechsler Intelligence Scale for Children - Fifth Edition (WISC-V). Information about how the tests function and differ in this overlapping age range is limited. Using a between-subjects design, the present study compared the cognitive profiles of typically developing Swedish-speaking children in Finland in this overlapping age range (6:1 - 7:2 years), assessed with the Swedish versions of either WPPSI-IV (n = 38) or WISC-V (n = 24). Profile analyses and one-way ANCOVA were performed to investigate differences in the comparable subtests, indexes and Full Scale IQ. On the subtest level, children assessed with WISC-V had significantly lower scores on the subtests Vocabulary, Matrix Reasoning, and Bug/Symbol Search compared to children assessed with WPPSI-IV. On the index level, scores for the Verbal Comprehension Index and the Fluid Reasoning Index were significantly lower for children assessed with WISC-V. The Full Scale IQ was significantly lower on WISC-V. Taken together, the findings indicate that WPPSI-IV and WISC-V produce partly different cognitive profiles. These differences are important to recognize when choosing which test to use and when interpreting the results of clinical assessments of children in this age group.