Text and Data Mining valid from 2019-08-13
Received: 20 November 2018
Accepted: 25 July 2019
First Online: 13 August 2019
Ethics approval and consent to participate
: All participants received written information and signed an informed consent form. The study was approved by the Norwegian Regional Committee for Medical Research Ethics (South-East) and the Norwegian Social Science Data Services.
: Not applicable. The manuscript does not contain data from any individual person.
: The authors declare that they have no competing interests.