Funding for this research was provided by:
National Natural Science Foundation of China (81803334, 71974212)
National Natural Science Foundation of China (71774178)
National Major Science and Technology Projects of China (2018ZX10715004)
Science and Technology Planning Project of Guangdong Province (2017A020212006)
Science and Technology Research Project of Guangzhou (201607010332, 201607010368)
Received: 23 September 2019
Accepted: 24 December 2019
First Online: 3 January 2020
Ethics approval and consent to participate
: Ethics approval was obtained from the ethics committee of Sun Yat-sen University (Approval No.  049). Informed consents were obtained online from the eligible participants before self-administering the questionnaire by clicking a box (“I agree to participate in this study”) of the online questionnaire.
: Not applicable.
: The authors declare that they have no competing interests.