TY - JOUR
T1 - Association between Elevated Iodine Intake and IQ among School Children in Portugal
AU - Carvalho, Irene P.
AU - Peixoto, Bruno
AU - Caldas, José Carlos
AU - Costa, Ana
AU - Silva, Sofia
AU - Moreira, Bárbara
AU - Almeida, Agostinho
AU - Moreira-Rosário, André
AU - Guerra, António
AU - Delerue-Matos, Cristina
AU - Sintra, Diana
AU - Pestana, Diogo
AU - Pinto, Edgar
AU - Mendes, Francisca Castro
AU - Martins, Inês
AU - Leite, João Costa
AU - Fontoura, Manuel
AU - Maia, Maria Luz
AU - Queirós, Pedro
AU - Moreira, Roxana
AU - Leal, Sandra
AU - Norberto, Sónia
AU - Costa, Vera
AU - Fernandes, Virgínia Cruz
AU - Keating, Elisa
AU - Azevedo, Luís
AU - Calhau, Conceição
N1 - Funding Information:
This project was funded through grants by the Public Health Initiatives Programme (PT06), financed by EEA Grants Financial Mechanism 2009–2014, and supported by FEDER through the operation POCI-01-0145-FEDER-007746 funded by the Programa Operacional Competitividade e Internacionalização—COMPETE2020 and by National Funds through FCT—Fundação para a Ciência e a Tecnologia, I.P., within CINTESIS, R&D Unit (reference UIDP/4255/2020) and within the scope of the project RISE, Associated Laboratory (reference LA/P/0053/2020). DP and VCF also received individual funding from Fundação para a Ciência e a Tecnologia (SFRH/BPD/109158/2015 in the first case; SFRH/BPD/109153/2015, UIDB/50006/2020, UIDP/50006/2020, and LA/P/0008/2020 in the second case).
PY - 2022/11
Y1 - 2022/11
N2 - 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.
AB - 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.
KW - cognition
KW - excessive iodine
KW - iodine-adequate population
KW - representative sample
KW - school ages
UR - http://www.scopus.com/inward/record.url?scp=85141602388&partnerID=8YFLogxK
U2 - 10.3390/nu14214493
DO - 10.3390/nu14214493
M3 - Article
C2 - 36364754
AN - SCOPUS:85141602388
SN - 1422-8599
VL - 14
JO - Nutrients
JF - Nutrients
IS - 21
M1 - 4493
ER -