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Article History

Received: 8 May 2018

Accepted: 31 October 2018

First Online: 11 December 2018

Ethics approval and consent to participate

: Cohort 1a: Prior to the study, the parents to the involved students received a letter including information about the project. Participation did not require parental consent, but the parents were informed that they could initially, or at any time later, decline their child’s participation. This form of passive consent was reviewed by the Regional Committee for Health Research Ethics with the rest of the project protocol. The conclusion was that the project was acceptable according to Danish legislation and did not require formal approval because all tests were non-invasive and there were no physical intervention involved []. The study was approved by the Danish Data Protection Agency (J-no. 2010-41-5147).Cohort 1b: Ethics committee approval was obtained before the start of the project (ID S20080047) and it was approved by the Danish Data Protection Agency (J-no. 2008-41-2240). Since this was not a randomized controlled clinical trial, the study is not suitable for registration in any of the clinical trial registers.All parents or guardians provided informed written consent for the family to participate in the study. In relation to children, all participation was voluntary; children could at any time withdraw from the whole project or from any part of it.Cohort 2: The local ethics committee found that the study did not need approval, since there was no intervention involved, which is in line with Danish law []. Documentation is available upon request. The project was approved by the Danish Data Protection Agency (J-no. 2004-41-4763 and J-no. 2010-41-5163).At the initial consultation, the patient was given oral and written information about the prospective study, an invitation to participate and a baseline questionnaire, including a consent form. Thus, written consent was given by returning the questionnaire.

: Not applicable.

: The authors declare that they have no competing interests.

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