Received: 15 March 2019
Accepted: 14 November 2019
First Online: 17 December 2019
Ethics approval and consent to participate
: This study was approved by The Regional Committee of Medical and Health Research Ethics in northern Norway (REK North), as part of the Tromsø Study Fit Futures cohort. Written consent was obtained from all participants aged ≥16 years. Those under 16 years of age brought signed, written consent from their parent or legal guardian.
: Not applicable
: The authors declare that they have no competing interests.