Text and Data Mining valid from 2018-04-18
Received: 29 December 2017
Accepted: 2 April 2018
First Online: 18 April 2018
Ethics approval and consent to participate
: The study protocols were approved by the Regional Committee for Medical and Health Research Ethics–North Norway (REK Nord 74/2001, 52/2005, and 105/2008) and an informed written consent was obtained from each participant.
: Not applicable.
: The authors declare that they have no competing interests.
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