Article History
First Online: 2 July 2018
Compliance with Ethical Standards
: The study protocol was approved by the Norwegian Regional Ethical Committee for Medical Research (ref. 2381-2015), South-Eastern Norway.
: The authors declare that they have no conflict of interest.
: All procedures involving participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and later amendments.
: Informed consent was obtained from all individual participants included in the study.