qian zhang department of respiratory medicine, affiliated changzhou no.2 people’s hospital, nanjing medical university, changzhou, china and department of respiratory medicine, nanjing general hospital of nanjing military command, nanjing, china fen-hong qian department of respiratory medicine, affiliated jiangbing hospital, jiangsu university, zhenjiang, china xiao-wei yin department of respiratory medicine, affiliated changzhou no.2 people’s hospital, nanjing medical university, changzhou, china qi cao department of respiratory medicine, affiliated changzhou no.2 people’s hospital, nanjing medical university, changzhou, china jian-ling bai department of epidemiology and biostatistics, school of public health, nanjing medical university, nanjing, china qiang du department of respiratory medicine, second affiliated hospital, nanjing medical university, nanjing , china