Document is current

Article History

Received: 2 February 2018

Accepted: 25 July 2018

First Online: 15 August 2018

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.

: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.