Table 1. Baseline characteristics of the participants.
| All participants (n = 12,631) | |
|---|---|
| Male | 5,400 (42.8) |
| Age, yr (median[range]) | 55.0 (40–91) |
| Smoking status | |
| Never | 7,514 (59.5) |
| Former | 1,850 (14.6) |
| Current | 3,267 (25.9) |
| Smoking history, pack-years | |
| Never | 7,514 (59.5) |
| 0.1−9.9 | 1,288 (10.2) |
| 10−19.9 | 1,128 (8.9) |
| 20−29.9 | 1,101 (8.7) |
| 30−39.9 | 764 (6.0) |
| 40+ | 836 (6.6) |
| Asthma | 563 (4.5) |
| Chest radiograph | |
| Normal | 11,583 (91.7) |
| Inactive TB | 1,048 (8.3) |
| BMI, kg/m2 (mean±SD) | 24.3 ± 3.0 |
| Chronic bronchitis* | 610 (7.3) |
| Wheezing (ever experienced) | 1,047 (8.3) |
| Education level (highest degree) | |
| Elementary school | 4,091 (32.4) |
| Middle school | 2,013 (16.0) |
| High school | 3,918 (31.1) |
| Above university | 2,596 (20.6) |
| Pulmonary function test | |
| FVC, L (mean ± SD) | 3.45 ± 0.84 |
| % predicted (mean ± SD) | 92.97 ± 11.68 |
| FEV1,L (mean ± SD) | 2.68 ± 0.67 |
| % predicted (mean ± SD) | 92.82 ± 13.32 |
| FEV1/FVC (mean ± SD) | 0.78 ± 0.07 |
Definition of abbreviations; PY pack-years, BMI body mass index, FVC forced vital capacity, FEV1forced expiratory volume in one second
*Cough or sputum for more than three months within a year. Proportion is calculated after excluding 4,324 participants without answer.
Values are represented as number (%), or mean ± standard deviation unless otherwise stated.