Received: 11 January 2019
Accepted: 30 July 2019
First Online: 7 August 2019
Ethics approval and consent to participate
: The Regional Committees for Medical and Health Research Ethics, Region South-East Norway, ref. no. 2015/1257, approved the study.
: When approved by the Regional Committees for Medical and Health Research Ethics, the information included in the registry data was given exemption from the requirement of informed consent.
: The authors declare that they have no competing interests.