Prenatal iodine nutrition and child attention deficit-hyperactivity disorder
| ISRCTN | ISRCTN41848933 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN41848933 |
| Protocol serial number | PDB1380 |
| Sponsors | The Research Council of Norway, TINE SA |
| Funders | Helse- og Omsorgsdepartementet, Utdannings- og forskningsdepartementet, National Institute of Environmental Health Sciences (contract no N01-ES-75558), National Institute of Neurological Disorders and Stroke (grant no.1 UO1 NS 047537-01 and grant no.2 UO1 NS 047537-06A1) |
- 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
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
Contact information
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 ID |
0000-0001-6315-7134 |
|---|
Study information
| Primary study design | Observational |
|---|---|
| Study design | Observational population-based prospective pregnancy cohort |
| Secondary study design | Epidemiological study |
| Study type | Participant information sheet |
| Scientific title | Maternal iodine intake and offspring attention deficit-hyperactivity disorder |
| Study objectives | The 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) studied | Child ADHD diagnosis and maternally reported child ADHD symptoms at age 8 years |
| Intervention | 1. 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 type | Other |
| Primary outcome measure(s) |
1. 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 |
| Key secondary outcome measure(s) |
No secondary outcome measures |
| Completion date | 31/12/2017 |
Eligibility
| Participant type(s) | |
|---|---|
| Age group | Mixed |
| Sex | All |
| Target sample size at registration | 77164 |
| Total final enrolment | 77164 |
| Key inclusion criteria | 1. 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 criteria | 1. 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 enrolment | 01/03/2002 |
| Date of final enrolment | 31/12/2008 |
Locations
Countries of recruitment
- Norway
Study participating centre
Oslo
NO-0213
Norway
Results and Publications
| Individual participant data (IPD) Intention to share | Yes |
|---|---|
| IPD sharing plan summary | Available on request |
| IPD sharing plan | Current 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 | |
| Results article | 10/04/2016 | 23/08/2022 | Yes | No | |
| Participant information sheet | 24/08/2022 | No | Yes | ||
| Participant information sheet | Participant information sheet | 11/11/2025 | 11/11/2025 | No | Yes |
| Protocol (other) | 23/08/2022 | No | No | ||
| Study website | Study website | 11/11/2025 | 11/11/2025 | 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.
