Funding for this research was provided by:
Natural Science Foundation of China (71673191)
Article History
Received: 26 March 2020
Accepted: 2 December 2020
First Online: 9 December 2020
Ethics approval and consent to participate
: The study protocol was approved by the Institutional Review Board of the Capital Institute of Pediatrics, Beijing, China (SHERLL number 2016015). Each participant provided their written consent prior to data collection.
: Not applicable.
: The authors declare that they have no competing interests.