Received: 4 October 2018
Accepted: 21 January 2019
First Online: 1 February 2019
Ethics approval and consent to participate
: The Ethics Committee for Human Research of Toujinkai Hospital approved this study [2018-05]. We did not explain the study to each patient because this study was a retrospective epidemiological study. We used the patient's medical record only. The participants’ information \was anonymized, so that individuals could not be identified from the medical records. The study was performed in accordance with the principles of the declaration of Helsinki.
: Not applicable
: The authors declare that they have no competing interests.
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