Text and Data Mining valid from 2020-03-06
Received: 16 October 2019
Accepted: 4 February 2020
First Online: 6 March 2020
Ethics approval and consent to participate
: This study was approved by the Ethical committee for medical research at Umeå University, Medical faculty, Sweden,; Reference Number Dnr: 2018/158–31. Written consent from each parent was retrieved.
: Not applicable.
: The authors declare that they have no competing interests.