Received: 27 March 2018
Accepted: 25 July 2018
First Online: 8 August 2018
Ethics approval and consent to participate
: The Regional Committee for Medical and Health Research Ethics granted approval for the research project (REK 2014/1970), and both registry owners approved their data to be utilised. As the study utilised existing registry data, no written or verbal consent to participate was required.
: Not applicable.
: The authors declare that they have no competing interests.
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