Funding for this research was provided by:
Received: 14 August 2020
Accepted: 10 February 2021
First Online: 16 March 2021
: F. Heilmann, P. Weigel and R. Wollny declare that they have no competing interests.
: The study is conducted in accordance with the Declaration of Helsinki on Ethical Principles for Medical Research Involving Human Subjects, adopted by the General Assembly of the World Medical Association (1996).