Received: 16 October 2019
Accepted: 13 March 2020
First Online: 27 May 2020
Ethics approval and consent to participate
: China Health and Nutrition Survey (CHNS) was approved by Carolina Population Center at the University of North Carolina at Chapel Hill and the National Institute for Nutrition and Health at the Chinese Center for Disease Control and Prevention. All participants provided written informed consent.
: This original research article has been submitted to this journal and is not under consideration by other publications.
: The authors declare that they have no competing interests.