1. Department of Epidemiology and Biostatistics, University of Georgia College of Public Health, Athens, Georgia, USA
2. Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, USA
3. Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana, USA
4. Clinical Epidemiology and Tobacco Dependence Treatment Research Department, Beijing Institute of Respiratory Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
5. Institute of Clinical Medical Science, China-Japan Friendship Hospital, Beijing, China