Received: 18 March 2019
Accepted: 27 May 2019
First Online: 7 June 2019
Ethics approval and consent to participate
: Scientific evaluation of this research database received a positive assessment by the Central Ethics Commission of the University of Witten/Herdecke (no. 201/2015). As data were anonymised informed consent was not obtainable and thus waived by the ethics committee.
: Not applicable.
: The authors declare that they have no competing interests.