Received: 1 April 2019
Accepted: 3 June 2019
First Online: 19 June 2019
Ethics approval and consent to participate
: The present study was evaluated and approved by the institutional ethics committee (Ethics Committee of the Friedrich-Alexander University Erlangen-Nürnberg; reference number: 4590). Written informed consent was obtained from all individual participants included in the study.
: Not applicable.
: The authors declare that they have no competing interests.