Funding for this research was provided by:
AIA Company limited
Received: 5 May 2020
Accepted: 19 August 2020
First Online: 3 September 2020
Ethics approval and consent to participate
: This study was approved by the Peking University (Ethical approval number: IRB00001052–18055). Informed consent obtained from online.
: Not applicable.
: We declare no conflicts of interest.