Funding for this research was provided by:
the National Key Research and Development Project of China (2019YFC1710301; 2020YFC0846300)
Received: 3 November 2020
Accepted: 19 February 2021
First Online: 24 February 2021
Ethics approval and consent to participate
: The CLHLS was approved by the Ethical Review Committee of Peking University (IRB00001052–13074). All participants signed the informed consent at the time of participation. The research has been performed in accordance with the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.