Received: 20 July 2018
Accepted: 2 May 2019
First Online: 24 May 2019
Ethics approval and consent to participate
: This study was conducted in accordance with the Declaration of Helsinki. The KNHANES was approved by the institutional review board at the Korea Center for Disease Control and Prevention (nos. 2010-02CON-21-C; 2011-02CON-06-C; 2012-01EXP-01-2C; 2013-07CON-03-4C; 2013-12EXP-03-5C; and 2015-01-02-6C) from 2010 to 2015. All the data collection and surveys were conducted with the participant’s written consent.
: Not applicable.
: The authors declare that they have no competing interests.
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