Funding for this research was provided by:
National Science Foundation of China (71003067, 71473152, 71774104)
the China Medical Board (16-257)
Cheeloo Youth Scholar Grant (IFYT1810)
Shandong University (IFYT181031)
Received: 11 March 2020
Accepted: 16 February 2021
First Online: 6 March 2021
Ethics approval and consent to participate
: This research was approved by the Institutional Review Board of the University of North Carolina at Chapel Hill and the National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention. All participants gave written informed consent for their participation in the survey.
: Not applicable.
: The authors declare that they have no competing interests.