Table 2.
Lung function and socioeconomic characteristics according to subtypes of subjects with mild-to-moderate airflow limitation identified by k-means clustering for k=5 clusters
| N | All
|
COPD-overlap
|
COPD
|
Asthmatic
|
Near-normal
|
Asthmatic-overlap
|
P-value |
|---|---|---|---|---|---|---|---|
| 2,140 | 586 | 37 | 392 | 232 | 893 | ||
| Spirometry | |||||||
| FEV1 % predicted | 80.9±12.1 | 80.3±10.9 | 80.5±13.3 | 77.8±9.7 | 101.5±7.9 | 77.3±8.9 | <0.001 |
| FVC% predicted | 92.5±12.7 | 92±11.8 | 89.9±14.5 | 96.6±11.2 | 107.1±10.8 | 87.3±10.5 | <0.001 |
| FEV1/FVC | 0.64±0.05 | 0.64±0.06 | 0.64±0.06 | 0.66±0.04 | 0.67±0.03 | 0.64±0.05 | <0.001 |
| FEV1/FVC < LLN | 1,226 (57) | 309 (53) | 16 (43) | 362 (92) | 57 (25) | 482 (54) | <0.001 |
| FEV1 ≥80% predicted | 1,060 (50) | 276 (47) | 17 (46) | 157 (40) | 232 (100) | 378 (42) | <0.001 |
| FEV1 <80% predicted | 1,080 (51) | 310 (53) | 20 (54) | 235 (60) | 0 (0) | 515 (58) | |
| Past history of asthma | 208 (10) | 42 (7) | 0 (0) | 46 (12) | 15 (7) | 105 (12) | 0.002 |
| Past history of tuberculosis | 269 (13) | 78 (13) | 3 (8) | 50 (13) | 21 (9) | 117 (13) | 0.43 |
| Education duration, years | <0.001 | ||||||
| ≥6 and <9 | 883 (41) | 236 (40) | 20 (54) | 49 (13) | 131 (57) | 447 (50) | |
| ≥9 and <12 | 369 (17) | 106 (18) | 7 (19) | 57 (15) | 39 (17) | 160 (18) | |
| ≥12 and <16 | 540 (25) | 162 (28) | 6 (16) | 153 (39) | 41 (18) | 178 (20) | |
| ≥16 | 344 (16) | 82 (14) | 4 (11) | 133 (34) | 21 (9) | 104 (12) | |
| Household income | <0.001 | ||||||
| First quartile | 536 (25) | 127 (22) | 12 (32) | 24 (6) | 93 (40) | 280 (31) | |
| Second quartile | 534 (25) | 156 (27) | 6 (16) | 68 (17) | 65 (28) | 239 (27) | |
| Third quartile | 536 (25) | 152 (26) | 10 (27) | 128 (33) | 43 (19) | 203 (23) | |
| Fourth quartile | 534 (25) | 151 (26) | 9 (24) | 172 (44) | 31 (13) | 171 (19) | |
| EQ-5D index | 0.91±0.14 | 0.92±0.13 | 0.91±0.11 | 0.96±0.08 | 0.87±0.18 | 0.89±0.16 | <0.001 |
Notes: Data are presented as mean ± SD or number (%). LLN prediction equations: 125.77628–0.36304× age (years) −0.17146× height (cm) for male; 97.36197–0.26015× age (years) −0.01861× height (cm) for female.
Abbreviations: COPD, chronic obstructive pulmonary disease; EQ-5D, The EuroQoL five dimensions questionnaire; SD, standard deviation; LLN, lower limit of normal; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity.