Funding for this research was provided by:
Norges Forskningsråd (208173/O30)
Text and Data Mining valid from 2018-05-31
Received: 7 August 2017
Accepted: 7 May 2018
First Online: 31 May 2018
Ethics approval and consent to participate
: The present study is based on retrospective analysis of registry data. The Regional Committees for Medical and Health Research Ethics (REK) of Mid-Norway approved the study and the data linkage procedures (permission 2011/783). The ethic committee REK formally waived the need for consent. The exemptions were given because our study used data registries where the information was collected from sources other than the persons themselves.
: The authors declare that they have no competing interests.
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