1. Department of Epidemiology and BiostatisticsSchool of Public Health, Nanjing Medical UniversityNanjing China
2. Department of Epidemiology and BiostatisticsSchool of Public Health, Peking University Health Science CenterBeijing China
3. Chinese Academy of Medical SciencesBeijing China
4. Clinical Trial Service Unit & Epidemiological Studies Unit (CTSU)Nuffield Department of Population Health, University of OxfordOxford United Kingdom