Funding for this research was provided by:
Norges Forskningsråd (237831, 218368)
Text and Data Mining valid from 2018-04-27
Received: 24 February 2017
Accepted: 6 April 2018
First Online: 27 April 2018
Ethics approval and consent to participate
: Data on human participants come from national population-wide registries, data which use is exempt from individual consent, but restrictions apply to the availability of these data. Use of the data was approved and licensed by Regional Committees for Medical And Health Research Ethics (REK) for the project code 2011/258 (S-06028a).
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.