Text and Data Mining valid from 2018-10-12
Received: 6 August 2018
Accepted: 3 October 2018
First Online: 12 October 2018
Ethics approval and consent to participate
: The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the institutional review committee of Fukushima Medical University (Fukushima, Japan; IRB number #2399).
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.