Received: 20 February 2020
Accepted: 19 May 2020
First Online: 26 May 2020
Ethics approval and consent to participate
: The study was approved by the Regional Committees for Medical and Health Research Ethics South East Norway in 2017 (reference 2016/417/REK) including waiver of participant’s individual consent.
: Not Applicable.
: The authors declare that they have no competing interests.