Received: 6 September 2017
Accepted: 24 May 2018
First Online: 7 June 2018
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of the School of Public Health, Dalian Medical University, and verbal consent was obtained from each participant. The ethical review boards approved the protocol because the data were health check-up data and the names of individuals involved in this study were not revealed. The consent processes were documented through audio recorder pens.
: The authors declare that they have no competing interests.
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