S-Y Li1,2, A A Qureshi2,3,4, W-Q Li2,3. 1. Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, China. 2. Department of Dermatology, Warren Alpert Medical School, Brown University, Providence, RI, U.S.A. 3. Department of Epidemiology, School of Public Health, Brown University, Providence, RI, U.S.A. 4. Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, U.S.A.