Received: 28 October 2019
Revised: 5 February 2020
Accepted: 19 February 2020
First Online: 2 March 2020
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: The study was conducted under the Declaration of Helsinki (2008) and approved by the local ethics committee of Vienna (protocol number: EK-11-117-0711). All participants signed an informed consent.