[1] Beijing Hospital,Department of Geriatrics
[2] National Center of Gerontology,Tobacco Medicine and Tobacco Cessation Centre, Center of Respiratory Medicine
[3] China-Japan Friendship Hospital; WHO Collaborating Centre for Tobacco Cessation and Respiratory Diseases Prevention; National Clinical Research Center for Respiratory Diseases,Department of Laboratory Medicine
[4] Beijing Hospital,Department of Respiratory and Critical Care Medicine
[5] Beijing Hospital,Statistics Department
[6] First Hospital of Peking University,undefined