Of the 37,753 subjects enrolled in KNHANES between 2008 and
2011, 3861 (10.2%) met the study criteria. Of these 239 cases (6.2%)
were excluded for following reasons: 4 participants had a history
of lung cancer, 6 had a history of pulmonary tuberculosis, and 229
did not have covariate information. Finally, 3622 participants were
included in the analysis