Table 1.
Characteristics of study participants
| Characteristic | Total sample (n=2445) |
Reference test positive (n=333) |
Reference test negative (n=2112) |
| Male sex, n (%) | 956 (39.1%) | 199 (59.8%) | 757 (35.8%) |
| Age in years; mean (SD) | 59.8 (9.6) | 63.5 (8.9) | 59.2 (9.6) |
| BMI; mean (SD) | 24.9 (3.5) | 24.3 (3.4) | 25.0 (3.4) |
| Education, n (%) | |||
| High school or below | 1879 (76.9) | 277 (83.2%) | 1602 (75.9%) |
| Above high school | 566 (23.1) | 56 (16.8%) | 510 (24.1%) |
| Employment status, n (%) | |||
| Employed | 674 (27.6%) | 54 (16.2%) | 620 (29.4%) |
| Unemployed | 665 (27.2%) | 98 (29.4%) | 567 (26.9%) |
| Retired | 1106 (45.2%) | 181 (54.4%) | 925 (43.8%) |
| Living in urban areas; n (%) | 1338 (54.7%) | 174 (52.3%) | 1164 (55.1%) |
| Smoking status, n (%) | |||
| Current smoker | 472 (19.3%) | 113 (33.9%) | 359 (17.0%) |
| Ex-smoker | 289 (11.8%) | 72 (21.6%) | 217 (10.3%) |
| Never smoker | 1684 (68.9%) | 148 (44.5%) | 1536 (72.7%) |
| Male | -- | 27 (18.2%) | -- |
| Female | -- | 121 (81.8%) | -- |
| Pack years; mean (SD) | 9.0 (17.8) | 18.0 (21.0) | 7.6 (16.8) |
| Health in general, n (%) | |||
| Very good-good | 1255 (51.3%) | 127 (38.1%) | 1128 (53.4%) |
| Fair-very bad | 1190 (48.7%) | 206 (61.9%) | 984 (46.6%) |
| Diagnosed conditions, n (%) | |||
| COPD | 88 (3.6%) | 64 (19.2%) | 24 (1.1%) |
| Chronic bronchitis/emphysema | 205 (8.4%) | 93 (27.9%) | 112 (5.3%) |
| Asthma | 105 (4.3%) | 48 (14.4%) | 57 (2.7%) |
| Tuberculosis | 41 (1.7%) | 12 (3.6%) | 29 (1.4%) |
| Hypertension | 842 (34.4%) | 119 (35.7%) | 723 (34.2%) |
| Diabetes mellitus | 330 (13.5%) | 43 (12.9%) | 287 (13.6%) |
| Heart disease | 274 (11.2%) | 43 (12.9%) | 231 (10.9%) |
| Other | 269 (11.0%) | 31 (9.3%) | 238 (11.3%) |
| None of the above | 1142 (46.7%) | 106 (31.8%) | 1036 (49.1%) |
| Symptoms, n (%) | |||
| At least occasional wheeze | 322 (13.2) | 110 (33.0) | 212 (10.0) |
| Productive cough | 457 (18.7) | 117 (35.1) | 340 (16.1) |
| mMRC, n (%) | |||
| Grade 0–1 | 2222 (90.9%) | 257 (77.2%) | 1965 (93.0%) |
| Grade 2–4 | 223 (9.1%) | 76 (22.8%) | 147 (7.0%) |
| CAT, mean (SD) | 6.1 (5.4%) | 8.9 (6.9%) | 5.6 (4.9%) |
| Bronchitis, pneumonia or severe whooping cough in childhood | 169 (6.9%) | 38 (11.4%) | 131 (6.2%) |
| Tuberculosis in childhood | 45 (1.8%) | 11 (3.3%) | 34 (1.6%) |
| Exposure to pollutants*, n (%) | |||
| Current/past exposure | 2256 (92.3%) | 307 (92.2%) | 1949 (92.3%) |
| Never | 189 (7.7%) | 26 (7.8%) | 163 (7.7%) |
| Year(s) of exposure, mean (SD) | 8.9 (6.4) | 9.1 (6.6) | 8.8 (6.4) |
| GOLD stage if <LLN, n (%) | |||
| I (FEV1 ≥80% predicted) | -- | 158 (47. 5%) | -- |
| II (FEV1 50%–79% predicted) | -- | 137 (41.1%) | -- |
| III (FEV1 30%–49% predicted) | -- | 33 (9.9%) | -- |
| IV (FEV1 <30% predicted) | -- | 5 (1.5%) | -- |
*Cooking fumes, biomass smoking, gas, steams, dust.
BMI, body mass index; CAT, COPD Assessment Test; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in one second; GOLD, global initiative for chronic obstructive lung disease; LLN, lower limit of normal; mMRC, modified medical research council dyspnea scale.