Funding for this research was provided by:
National Natural Science Foundation of China (NSFC81402692)
Received: 5 February 2019
Accepted: 29 April 2019
First Online: 10 June 2019
Ethics approval and consent to participate
: The GRECF study was approved by the Institute Review Board at the Peking University Health Science Center.
: All participants have signed consent forms.
: The authors declare that they have no competing interests.
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