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Preconception maternal iodine status is positively associated with IQ but not with measures of executive function in childhood

Preconception maternal iodine status is positively associated with IQ but not with measures of executive function in childhood
Preconception maternal iodine status is positively associated with IQ but not with measures of executive function in childhood

Background: adverse effects of severe maternal iodine deficiency in pregnancy on fetal brain development are wellestablished, but the effects of milder deficiency are uncertain. Most studies examine iodine status in pregnancy; less is known about iodine nutrition before conception. 

Objective: we examined relations between maternal preconception iodine status and offspring cognitive function, within a prospective mother-offspring cohort. 

Methods: maternal iodine status was assessed through the use of the ratio of iodine:creatinine concentrations (I/Cr) in spot urine samples [median (IQR) period before conception 3.3 y (2.2-4.7 y)]. Childhood cognitive function was assessed at age 6-7 y. Full-scale IQ was assessed via the Wechsler Abbreviated Scale of Intelligence, and executive function through the use of tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Analyses (n = 654 mother-child dyads) were adjusted for potential confounders including maternal intelligence, education, and breastfeeding duration. 

Results: the median (IQR) urinary iodine concentration was 108.4 μg/L (62.2-167.8 μg/L) and the I/Cr ratio 114 μg/g (76- 164 μg/g). The preconception I/Cr ratio was positively associated with child IQ, before and after adjustment for potential confounding influences [β = 0.13 (95% CI: 0.04, 0.21)/SD, P = 0.003]. 8.9% of women had a preconception urinary I/Cr ratio < 50 μg/g; compared with those with an I/Cr ratio ≥150 μg/g, the IQ of their offspring was 0.49 (95% CI: 0.79, 0.18) SD lower. There were no associations with the executive function outcomes assessed via CANTAB, before or after adjustment for confounders. 

Conclusions: the positive association between iodine status before conception and child IQ provides some support for demonstrated links between low maternal iodine status in pregnancy and poorer cognitive function reported in other studies. However, given the negative effects on school performance previously observed in children born to iodine-deficient mothers, the lack of associations with measures of executive function in the present study was unexpected. Further data are needed to establish the public health importance of low preconception iodine status.

Cognition, Development, Iodine
0022-3166
959-966
Robinson, Sian
ba591c98-4380-456a-be8a-c452f992b69b
Crozier, Sarah
9c3595ce-45b0-44fa-8c4c-4c555e628a03
Miles, Elizabeth
20332899-ecdb-4214-95bc-922dde36d416
Gale, Catharine
5bb2abb3-7b53-42d6-8aa7-817e193140c8
Calder, Philip
1797e54f-378e-4dcb-80a4-3e30018f07a6
Cooper, Cyrus
e05f5612-b493-4273-9b71-9e0ce32bdad6
Inskip, Hazel
5fb4470a-9379-49b2-a533-9da8e61058b7
Godfrey, Keith
0931701e-fe2c-44b5-8f0d-ec5c7477a6fd
Robinson, Sian
ba591c98-4380-456a-be8a-c452f992b69b
Crozier, Sarah
9c3595ce-45b0-44fa-8c4c-4c555e628a03
Miles, Elizabeth
20332899-ecdb-4214-95bc-922dde36d416
Gale, Catharine
5bb2abb3-7b53-42d6-8aa7-817e193140c8
Calder, Philip
1797e54f-378e-4dcb-80a4-3e30018f07a6
Cooper, Cyrus
e05f5612-b493-4273-9b71-9e0ce32bdad6
Inskip, Hazel
5fb4470a-9379-49b2-a533-9da8e61058b7
Godfrey, Keith
0931701e-fe2c-44b5-8f0d-ec5c7477a6fd

Robinson, Sian, Crozier, Sarah, Miles, Elizabeth, Gale, Catharine, Calder, Philip, Cooper, Cyrus, Inskip, Hazel and Godfrey, Keith (2018) Preconception maternal iodine status is positively associated with IQ but not with measures of executive function in childhood. Journal of Nutrition, 148 (6), 959-966. (doi:10.1093/jn/nxy054).

Record type: Article

Abstract

Background: adverse effects of severe maternal iodine deficiency in pregnancy on fetal brain development are wellestablished, but the effects of milder deficiency are uncertain. Most studies examine iodine status in pregnancy; less is known about iodine nutrition before conception. 

Objective: we examined relations between maternal preconception iodine status and offspring cognitive function, within a prospective mother-offspring cohort. 

Methods: maternal iodine status was assessed through the use of the ratio of iodine:creatinine concentrations (I/Cr) in spot urine samples [median (IQR) period before conception 3.3 y (2.2-4.7 y)]. Childhood cognitive function was assessed at age 6-7 y. Full-scale IQ was assessed via the Wechsler Abbreviated Scale of Intelligence, and executive function through the use of tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Analyses (n = 654 mother-child dyads) were adjusted for potential confounders including maternal intelligence, education, and breastfeeding duration. 

Results: the median (IQR) urinary iodine concentration was 108.4 μg/L (62.2-167.8 μg/L) and the I/Cr ratio 114 μg/g (76- 164 μg/g). The preconception I/Cr ratio was positively associated with child IQ, before and after adjustment for potential confounding influences [β = 0.13 (95% CI: 0.04, 0.21)/SD, P = 0.003]. 8.9% of women had a preconception urinary I/Cr ratio < 50 μg/g; compared with those with an I/Cr ratio ≥150 μg/g, the IQ of their offspring was 0.49 (95% CI: 0.79, 0.18) SD lower. There were no associations with the executive function outcomes assessed via CANTAB, before or after adjustment for confounders. 

Conclusions: the positive association between iodine status before conception and child IQ provides some support for demonstrated links between low maternal iodine status in pregnancy and poorer cognitive function reported in other studies. However, given the negative effects on school performance previously observed in children born to iodine-deficient mothers, the lack of associations with measures of executive function in the present study was unexpected. Further data are needed to establish the public health importance of low preconception iodine status.

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Accepted/In Press date: 26 February 2018
e-pub ahead of print date: 15 May 2018
Published date: 1 June 2018
Keywords: Cognition, Development, Iodine

Identifiers

Local EPrints ID: 418520
URI: https://eprints.soton.ac.uk/id/eprint/418520
ISSN: 0022-3166
PURE UUID: 3254aba6-06c8-4017-b4ce-bb46f3b59abc
ORCID for Sian Robinson: ORCID iD orcid.org/0000-0003-1766-7269
ORCID for Sarah Crozier: ORCID iD orcid.org/0000-0002-9524-1127
ORCID for Elizabeth Miles: ORCID iD orcid.org/0000-0002-8643-0655
ORCID for Catharine Gale: ORCID iD orcid.org/0000-0002-3361-8638
ORCID for Cyrus Cooper: ORCID iD orcid.org/0000-0003-3510-0709
ORCID for Hazel Inskip: ORCID iD orcid.org/0000-0001-8897-1749
ORCID for Keith Godfrey: ORCID iD orcid.org/0000-0002-4643-0618

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Date deposited: 09 Mar 2018 17:31
Last modified: 10 Dec 2019 05:31

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Contributors

Author: Sian Robinson ORCID iD
Author: Sarah Crozier ORCID iD
Author: Elizabeth Miles ORCID iD
Author: Catharine Gale ORCID iD
Author: Philip Calder
Author: Cyrus Cooper ORCID iD
Author: Hazel Inskip ORCID iD
Author: Keith Godfrey ORCID iD

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