Funding for this research was provided by:
The University of Hong Kong Foundation for Educational Development and Research (SN/1f/HKUF-DC; C20400.28505200)
the Health Medical Research Fund in HongKong (HMRF/13143241)
the Guangzhou Public Health Bureau (201102A211004011)
the Guangzhou Science and Technology Bureau (2002Z2-E2051; 2012J5100041; 2013J4100031)
Natural Science Foundation of Guangdong and the University of Birmingham (2015A030313891)
Text and Data Mining valid from 2018-11-06
Received: 18 June 2018
Accepted: 26 September 2018
First Online: 6 November 2018
Ethics approval and consent to participate
: The GBCS was approved by Guangzhou Medical Ethics Committee of the Chinese Medical Association. All participants provided written, informed consent before participation.
: Not applicable
: The authors declare that they have no competing interests.
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