Funding for this research was provided by:
Shandong Medical and Health Science and Technology Development Project (2018WS060)
Chinese Scholarship Council
Article History
Received: 21 September 2020
Accepted: 14 December 2020
First Online: 30 December 2020
Ethics approval and consent to participate
: Research Ethics Committees of Peking University approved the CLHLS, and written informed consents from all participants or their representatives were collected.
: Not applicable.
: The authors declare that they have no competing interests.