Funding for this research was provided by:
National Science and Technology Planning Project (2008BAI58B05)
Received: 24 February 2020
Accepted: 24 August 2020
First Online: 19 September 2020
Ethics approval and consent to participate
: The study protocol was approved by the Ethical Review Committee of the National Institute for Nutrition and Food Safety, Chinese Centre for Disease Control and Prevention. Written informed consent was obtained from the next of kin, carers, or guardians of all the participants.
: Not applicable.
: The authors declare that they have no competing interests.