Received: 6 June 2019
Accepted: 22 November 2019
First Online: 10 December 2019
Ethics approval and consent to participate
: Ethics approval for this study was given by the Hannover Medical School (MHH) Ethics Committee on 25th May 2016 (Project ID: 3211–2016). All participants provided written consent.
: Not applicable.
: The authors declare that they have no competing interests in this study.