Table 1.
Baseline characteristics
| Parameter | Non-smokers | Smokers without airflow obstruction | Mild/Mod COPD | Severe COPD | P-value* |
|---|---|---|---|---|---|
| (n = 100) | (n = 199) | (n = 201) | (n = 200) | ||
| Age [IQI] | 56 [50, 65] | 61 [52, 67] | 66 [ 60, 71] | 65 [59, 71] | < 0.001 |
| Sex N (%) | |||||
| Male | 42 (42%) | 96 (48%) | 130 (65%) | 122 (61%) | < 0.001 |
| Race N (%) | < 0.001 | ||||
| Asian | 3 (3.1%) | 3 (1.5%) | 5 (2.5%) | 2 (1.0%) | |
| Black | 26 (27%) | 52 (27%) | 23 (12%) | 29 (15%) | |
| Other | 4 (4.1) | 8 (4.1%) | 4 (2.0%) | 4 (2.0%) | |
| White | 65 (66%) | 133 (68%) | 168 (84%) | 163 (82%) | |
| Current smoking N (%) | 0 (0%) | 98 (48%) | 77 (39%) | 40 (20%) | < 0.001 |
| FEV1% predicted [IQI] | 102 [95, 109] | 97 [86, 106] | 71 [61, 80] | 34 [27, 43] | < 0.001 |
| 6MWD [IQI] | 465 [392, 516] | 450 [390, 503] | 429 [366, 484] | 315 [249, 396] | < 0.001 |
| CAT [IQI] | 3 [1, 8] | 9 [5, 16] | 13 [8, 20] | 19 [13, 24] | < 0.001 |
| SGRQ [IQI] | 5 [4, 11] | 17 [8, 38] | 28 [16, 45] | 47 [39, 60] | < 0.001 |
IQI interquartile interval, FEV1 forced expiratory volume in 1 s, 6MWD six-minute walk distance, SGRQ St. George’s Respiratory Questionnaire, CAT COPD Assessment Test
*Kruskal–Wallis test, Chi-square test, or Fisher’s exact test comparing participants within each subgroup, as appropriate