Funding for this research was provided by:
Norges Forskningsråd (221047/F40)
Gjensidige Foundation (1042294)
Received: 26 March 2019
Accepted: 13 August 2019
First Online: 27 August 2019
Ethics approval and consent to participate
: The South-East Regional Committee for Medical Research Ethics approved the study protocol (reference number 2013/1893). We obtained written informed consent from each child’s parents or legal guardian and from the responsible school authorities prior to all testing.
: Not applicable.
: The authors declare that they have no competing interests.