Study population
The target subjects of the present study were participants in the CHNS, which is an ongoing open, prospective household-based study conducted since 1989 to investigate health risk factors, nutritional status, sociological, demographic transformation, and health-related outcomes of the myladyboydate Chinese population 16 . The CHNS cohort includes new household formation and replacement communities and households; all household members are studied. Furthermore, in-depth community data are collected. Detailed information about the sampling procedure on the cohort has been reported elsewhere, and they are used jointly and separately in hundreds of studies 17,18,19 . This study was reviewed and authorized by Institutional Review Boards of the University of North Carolina at Chapel Hill and the National Institute of Nutrition and Food Safety, China Center for Disease Control and Prevention. Due to its excellent properties such as stratified random sampling, large sample, and panel data, CHNS data has become the basic data of this study. All methods were performed under their relevant guidelines and regulations.