[1] Capital Med Univ, Beijing Friendship Hosp, Natl Clin Res Ctr Digest Dis, Beijing, Peoples R China
[2] Peking Univ, Sch Publ Hlth, Dept Epidemiol & Biostatist, Hlth Sci Ctr, Beijing, Peoples R China
[3] Univ Cambridge, Sch Clin Med, Primary Care Unit, Cambridge, England
[4] Peking Univ, Dept Endocrinol & Metab, Int Hosp, Beijing, Peoples R China