Prenatal iodine nutrition and child attention deficit-hyperactivity disorder

ISRCTN ISRCTN41848933
DOI https://doi.org/10.1186/ISRCTN41848933
Secondary identifying numbers PDB1380
Submission date
12/09/2017
Registration date
14/09/2017
Last edited
24/08/2022
Recruitment status
No longer recruiting
Overall study status
Completed
Condition category
Mental and Behavioural Disorders
Prospectively registered
Protocol
Statistical analysis plan
Results
Individual participant data

Plain English summary of protocol

Background and study aims
A lack of certain nutrients (deficiency) during critical phases in brain development may result in irreversible functional changes to the brain, the most critical period being pregnancy (gestation) and the early years of life. There is evidence for a link between low iodine levels during pregnancy and later attention-deficit/hyperactivity disorder (ADHD) in the child, but more studies are needed. Studies are also needed to explore whether iodine supplements in pregnancy can compensate for a lack of iodine in the diet. The WHO currently recommends the use of iodine supplements in pregnancy in areas where pregnant women are at risk of mild- to moderate iodine deficiency, but the recommendation lacks scientific support. Some studies even indicate that starting iodine supplementation in pregnancy might have negative effects. It is very important to clarify these relationships as soon as possible in order to design preventive strategies. The main aim of this study is to examine the possible link between iodine intake from food in pregnancy and the risk of ADHD in the child at age 8 years. A second aim is to explore the links between use of iodine-containing supplements before and during pregnancy and the risk of ADHD.

Who can participate?
Pregnant women in their first trimester recruited from all over Norway during the years 1999 to 2008

What does the study involve?
Participants’ iodine intake from food and use of iodine-containing supplements are assessed using questionnaires. ADHD symptoms of the children at age 8 years are assessed by questionnaire, and ADHD diagnoses are obtained from the Norwegian Patient Registry.

What are the possible benefits and risks of participating?
As this is an observational study there are no benefits or risks for the individual participants, but there is a potential large benefit for society and for future generations. The results from this study are communicated to participants through the study website and by newsletters to all participating families.

Where is the study run from?
Norwegian Institute of Public Health (Norway)

When is the study starting and how long is it expected to run for?
August 2016 to December 2017

Who is funding the study?
1. Norwegian Ministry of Health (Norway)
2. Norwegian Ministry of Education and Research (Norway)
3. National Institute of Environmental Health Sciences (USA)
4. National Institute of Neurological Disorders and Stroke (USA)

Who is the main contact?
Dr Anne-Lise Brantsaeter

Study website

Contact information

Dr Anne Lise Brantsaeter
Scientific

Department of Food Safety
Division of Climate and Environmental Health
Norwegian Institute of Public Health
PO Box 222 Skoyen
Oslo
NO-0213
Norway

ORCiD logoORCID ID 0000-0001-6315-7134

Study information

Study designObservational population-based prospective pregnancy cohort
Primary study designObservational
Secondary study designEpidemiological study
Study setting(s)Community
Study typeOther
Study type Participant information sheet
Scientific titleMaternal iodine intake and offspring attention deficit-hyperactivity disorder
Study objectivesThe main aim of the current study was to explore the association between iodine intake from food in pregnancy (as a proxy for long-term iodine intake and status) and i) risk of specialist-diagnosed ADHD in the child and ii) maternal report of child ADHD symptoms at age 8 years. A second aim was to explore the associations between maternal use of iodine-containing supplements prior to and during pregnancy and the same outcome measures.
Ethics approval(s)The Regional Committee for Medical Research Ethics South East Norway, 20/10/2016, ref: REK 2013/594
Health condition(s) or problem(s) studiedChild ADHD diagnosis and maternally reported child ADHD symptoms at age 8 years
Intervention1. Maternal iodine intake from food in non-users of supplemental iodine assessed by a food frequency questionnaire in gestational week 22
2. Maternal use of iodine-containing supplements (dosage and time of initiation) assessed by questionnaires in pregnancy (gestational week 17 and 22)
Intervention typeOther
Primary outcome measure1. Registered child ADHD diagnosis in the Norwegian Patient Registry (NPR) by Dec. 2015. From 2008, all government-owned and government-financed hospitals and outpatient clinics mandatorily report individual level diagnoses defined in the tenth revision of the International Classification of Disease (ICD-10) to the NPR in order to receive financial reimbursement. Using individual personal identification numbers, diagnostic information from NPR was linked to MoBa. Thus all MoBa children registered with an ICD-10-diagnosis of hyperkinetic disorder (HKD coded as F90.0, F90.1, F90.8, or F90.9) between 2008 and 2015 were identified and regarded as having ADHD
2. Child ADHD symptoms assessed in the 8 year questionnaire from MoBa on a 4-point Likert scale (never/rarely, sometimes, often, or very often) covering inattention problems (9 items) and hyperactivity/impulsivity (9 items) from the ADHD Rating Scale
Secondary outcome measuresNo secondary outcome measures
Overall study start date15/08/2016
Completion date31/12/2017

Eligibility

Participant type(s)Mixed
Age groupMixed
SexBoth
Target number of participantsThe total cohort includes more than 100,000 mother-child pairs. A total of 77,164 mother-child pairs were included in this study, and for 27,945 there were data on maternally reported ADHD score at child age 8 years
Total final enrolment77164
Key inclusion criteria1. Pregnant women in their first trimester recruited from all over Norway during the years 1999 to 2008 and asked to answer questionnaires (in Norwegian) at regular intervals during pregnancy and after birth
2. To be included in the current study mothers had to have responded to a general questionnaire around gestational week (GW) 17, and a food frequency questionnaire (FFQ) around GW 22
3. Only singleton pregnancies
4. Only participants with information on all covariates were included in the analysis because of the large sample size and low rates of missing values
5. Pregnant women at any age were allowed to participate
Key exclusion criteria1. Multiple pregnancies
2. Maternal use of thyroid medication in pregnancy
3. Missing information on important covariates
4. Children registered as dead or emigrated by Jan 2016
5. FFQs with more than 3 blank pages
6. Calculated energy intakes <4.5 MJ or >20 MJ
Date of first enrolment01/03/2002
Date of final enrolment31/12/2008

Locations

Countries of recruitment

  • Norway

Study participating centre

Norwegian Institute of Public Health
PO Box 222 Skoyen
Oslo
NO-0213
Norway

Sponsor information

The Research Council of Norway
Research council

Postboks 564
Lysaker
Oslo
1327
Norway

Phone +47 (0)22037000
Email post@forskningsradet.no
Website http://www.forskningsradet.no/en/Home_page/1177315753906
ROR logo "ROR" https://ror.org/00epmv149
TINE SA
Industry

Postboks 25
Oslo
0051
Norway

Funders

Funder type

Government

Helse- og Omsorgsdepartementet
Government organisation / National government
Alternative name(s)
Ministry of Health and Care Services
Location
Norway
Utdannings- og forskningsdepartementet
Government organisation / National government
Alternative name(s)
Norwegian Ministry of Education and Research, UFD
Location
Norway
National Institute of Environmental Health Sciences (contract no N01-ES-75558)
Government organisation / Research institutes and centers
Alternative name(s)
The National Institute of Environmental Health Sciences, NIH National Institute of Environmental Health Sciences, Division of Environmental Health Sciences, National Environmental Health Sciences Center, NIEHS, DEHS
Location
United States of America
National Institute of Neurological Disorders and Stroke (grant no.1 UO1 NS 047537-01 and grant no.2 UO1 NS 047537-06A1)
Government organisation / National government
Alternative name(s)
National Institute of Neurological Disorders & Stroke, NIH/National Institute of Neurological Disorders and Stroke, NIH National Institute of Neurological Disorders and Stroke, Instituto Nacional de Trastornos Neurológicos y Accidentes Cerebrovasculares, The National Institute of Neurological Disorders and Stroke, National Institute of Neurological Disorders and Blindness, National Institute of Neurological and Communicative Disorders and Stroke, NINDS, NINDB, NINCDS
Location
United States of America

Results and Publications

Intention to publish date01/12/2017
Individual participant data (IPD) Intention to shareYes
IPD sharing plan summaryAvailable on request
Publication and dissemination planProtocol: https://www.fhi.no/globalassets/dokumenterfiler/moba/pdf/moba-protocol-revised-oct-2012.pdf
This study will result in one publication in an international peer-reviewed journal.
IPD sharing planCurrent IPD sharing statement as of 24/08/2022:
The consent given by the participants does not allow for the storage of data on an individual level in repositories or journals. Researchers who want access to datasets for replication should apply through helsedata.no. Access to data sets requires approval from The Regional Committee for Medical and Health Research Ethics in Norway and an agreement with MoBa.

Previous IPD sharing statement:
No data can be shared because of data protection regulations. Other researchers, nationally and internationally, will have access to the cohort on request. For more information about research and data access from the Norwegian Mother and Child Cohort Study see: https://www.fhi.no/en/op/data-access-from-health-registries-health-studies-and-biobanks/data-from-moba/research-and-data-access/#protocol

Study outputs

Output type Details Date created Date added Peer reviewed? Patient-facing?
Results article results 13/11/2017 Yes No
Protocol (other) 23/08/2022 No No
Results article 10/04/2016 23/08/2022 Yes No
Participant information sheet 24/08/2022 No Yes

Editorial Notes

24/08/2022: The following changes were made to the trial record:
1. Participant information sheet and total final enrolment added.
2. IPD sharing statement and contact details updated.
3. The target number of participants was changed from 'A total of 77,164 mother-child pairs were included in this study, and for 27,945 there were data on maternally reported ADHD score at child age 8 years' to 'The total cohort includes more than 100,000 mother-child pairs. A total of 77,164 mother-child pairs were included in this study, and for 27,945 there were data on maternally reported ADHD score at child age 8 years'.
23/08/2022: Protocol and publication reference added.
03/08/2018: Publication reference added.