Received: 14 January 2020
Accepted: 17 May 2020
First Online: 24 May 2020
Ethics approval and consent to participate
: The project was reviewed by the Regional Committee for Medical and Health Research Ethics (REK) in Norway, who according to the Act on medical and health research (the Health Research Act 2008) concluded that the study did not require full review by REK. The study was approved by the Norwegian Centre for Research Data. Written informed consent from the participants and their parents or caretakers was obtained prior to the data collection.
: Not applicable.
: The authors declare that they have no competing interests.