Funding for this research was provided by:
Norwegian Directorate of Health
Text and Data Mining valid from 2019-06-26
Received: 22 February 2019
Accepted: 18 June 2019
First Online: 26 June 2019
Ethics approval and consent to participate
: The study was approved by the Norwegian centre for research data (NSD; reference no. 58038). Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.