Received: 7 December 2018
Accepted: 18 June 2019
First Online: 26 June 2019
Ethics approval and consent to participate
: Approved by the Regional Committees for Medical and Health Research Ethics - 12 February 2016, project no. 2468. Consent was deemed unnecessary by the Norwegian Centre for Research Data − 15 February 2016, project no. 45571.Each hospital’s local research committee approved the data collection.
: It was not possible to contact each patient because information on individual level was not available in the data.
: The authors declare that they have no competing interests.