Funding for this research was provided by:
National Key R&D Program of China (2017YFC1310902)
Received: 13 February 2018
Accepted: 31 May 2018
First Online: 31 July 2018
Ethics approval and consent to participate
: This research was ethically approved by National Center for Chronic and Non-communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention.
: The authors declare that they have no competing interests.
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