Received: 21 August 2020
Accepted: 24 November 2020
First Online: 7 January 2021
Ethics approval and consent to participate
: The requirement for informed consent was waived due to the anonymous nature of the data. Study approval was obtained from the Institutional Review Board of Saiseikai Utsunomiya Hospital (No. 2017–16).
: Not applicable.
: The authors declare that they have no conflicts of interest<i>.</i>