Text and Data Mining valid from 2019-08-13
Received: 13 February 2019
Accepted: 24 July 2019
First Online: 13 August 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: The medical ethics committee approved the original study and no informed consent was necessary because of the observational design.
: All authors meet all of the criteria of the International Committee of Medical Journal Editors (ICMJE).