Funding for this research was provided by:
Received: 15 July 2021
Accepted: 25 October 2021
First Online: 24 November 2021
: This study is retrospective in nature and uses only publicly available datasets. The local Ethics Committee (Ethik-Kommission, Medizinische Fakultät der Universität Duisburg-Essen, Germany) waived therefore the need for an ethics approval.
: Not applicable.
: The authors declare that they have no competing interests.