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Article History

Received: 26 September 2024

Accepted: 5 December 2025

First Online: 10 December 2025

Declarations

:

: This study was approved by the Ethics Committee of Gunma University (Approval No.: HS2020-002) and Takasaki University of Health and Welfare (Approval No.: 2007) and was conducted in accordance with the Declaration of Helsinki. This study was a retrospective study using data from the past 20 years, and it was difficult to obtain informed consent from all participants. Because this was a retrospective study using data collected since 2004, it was not feasible to obtain individual informed consent from all participants. Therefore, with approval from the institutional ethics committees, an opt-out approach was used, in which potential participants were considered to have agreed to participate unless they explicitly declined participation. In accordance with the committees’ instructions, information regarding the study purpose, subjects, and use of personal data was publicly disclosed on the hospital’s official website, and a contact point was provided to allow patients or their families to decline participation if they wished. This opt-out procedure is an ethically accepted and commonly used method for retrospective studies in Japan in which obtaining consent from all participants is impractical.

: Not applicable.

: The authors declare no competing interests.