[1] Capital Med Univ, Beijing Chao Yang Hosp, Dept Stomatol, 8 Gongti South Rd, Beijing 100020, Peoples R China
[2] Capital Med Univ, Beijing Chao Yang Hosp, Dept Clin Epidemiol, Beijing, Peoples R China
[3] Beijing Inst Resp Med, Beijing, Peoples R China
[4] Nova Southeastern Univ, Dept Oral Sci & Translat Res, Coll Dent Med, Ft Lauderdale, FL USA
[5] China Japan Friendship Hosp, Ctr Resp Med, Dept Pulm & Crit Care Med, 2 Yinghuayuan Dongjie, Beijing 100029, Peoples R China
[6] Natl Clin Res Ctr Resp Dis, Beijing, Peoples R China
[7] Peking Union Med Coll, Inst Resp Med, Beijing, Peoples R China
[8] Capital Med Univ, Dept Resp Med, Beijing, Peoples R China
[9] Beijing Chao Yang Hosp, Dept Pulm & Crit Care Med, Beijing Key Lab Resp & Pulm Circulat Disorders, Beijing, Peoples R China
[10] WHO Collaborating Ctr Tobacco Cessat & Resp Dis Pr, Beijing, Peoples R China