Text and Data Mining valid from 2018-08-06
Received: 23 February 2018
Accepted: 21 June 2018
First Online: 6 August 2018
Ethics approval and consent to participate
: The study was notified by Datatilsynet (the Danish Data Protection Agency). Danish law regarding questionnaire and register based studies do not require approval by ethical and scientific committees, nor informed consent to obtain and analyze individual data [CitationRef removed]. All data was de-identified and analyzed anonymously.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.