Received: 18 February 2019
Accepted: 19 July 2019
First Online: 31 July 2019
Ethics approval and consent to participate
: This study was approved by the Regional Medical Ethical Committee of South-East Norway (REK 2015/363). Moreover, all studied subjects gave their informed written consent to participate in the study.
: Consent for publication has been obtained from all participants.
: The authors declare that they have no competing interests.