Funding for this research was provided by:
the Chiba Foundation for Health Promotion & Disease Prevention (No. II-2, 2016)
Received: 17 May 2020
Accepted: 15 September 2020
First Online: 22 September 2020
Ethics approval and consent to participate
: This study protocol was approved by the Ethics Committees of Chiba University (No. 182) and the National Center for Global Health and Medicine (No. 1837). All participants were provided with a written informed consent form, and explanation and participation agreement were performed in accordance with the Declaration of Helsinki principles.
: Not applicable.
: The authors declare that they have no competing interests.