Article History
Received: 10 September 2019
Accepted: 4 January 2020
First Online: 14 January 2020
Compliance with ethical standards
:
: The authors declare that they have no conflicts of interest.
: All procedures in the study was conducted in accordance with the 1964 Helsinki declaration and its later amendments or comparable ethical standards and approved by the Regional Committee for Medical and Health Research Ethics, Health Region South-East, Norway (Ref. S-081266).
: Not applicable. This study is based on anonymized data, and permission to use the data was obtained from the project manager of the main study.