Table 1.
Baseline Characteristics in Smokers With Normal Spirometry Resultsa Stratified by Postbronchodilator FEV1/SVC < 0.7 (n = 854)
| Variable | Postbronchodilator FEV1/SVC ≥ 0.7 (n = 734) | Postbronchodilator FEV1/SVC < 0.7 (n = 120) | P Valueb |
|---|---|---|---|
| Age, y | 59.13 ± 9.59 | 65.35 ± 9.02 | < .001 |
| Female sex | 391 (53.3) | 51 (42.5) | .036 |
| White race | 489 (66.6) | 92 (76.7) | .037 |
| BMI, kg/m2 | 28.73 ± 5.05 | 29.12 ± 4.87 | .36 |
| Pack-years smoking | 40.75 ± 24.29 | 50.31 ± 22.93 | < .001 |
| Currently smoking | 387 (53.2) | 45 (38.1) | .003 |
| Asthma | 107 (14.6) | 19 (15.8) | .83 |
| Congestive heart failure | 10 (1.4) | 2 (1.7) | .68 |
| Diabetes mellitus | 77 (10.6) | 22 (18.5) | .019 |
| Hypertension | 296 (40.6) | 65 (54.6) | .006 |
| OSA | 130 (17.7) | 21 (17.5) | 1 |
| Stroke | 26 (3.6) | 4 (3.4) | 1 |
| History of exacerbation | 97 (13.3) | 14 (11.8) | .74 |
| Bronchodilators | 149 (20.3) | 32 (26.7) | .14 |
| Inhaled glucocorticoids | 76 (10.4) | 13 (10.8) | 1 |
| Chronic bronchitis | 259 (37.1) | 46 (41.8) | .40 |
| MMRC ≥ 2 | 93 (12.8) | 11 (9.2) | .34 |
| CAT score ≥ 10 | 332 (49.0) | 57 (49.6) | .99 |
| Prebronchodilator FEV1, L | 2.71 ± 0.68 | 2.56 ± 0.66 | .047 |
| Prebronchodilator FEV1 % predicted | 94.17 ± 12.90 | 89.17 ± 11.52 | < .001 |
| Prebronchodilator FVC, L | 3.61 ± 0.89 | 3.69 ± 0.97 | .34 |
| Prebronchodilator FVC % predicted | 96.97 ± 12.61 | 97.02 ± 12.01 | .76 |
| Postbronchodilator FEV1, L | 2.87 ± 0.70 | 2.70 ± 0.67 | .026 |
| Postbronchodilator FEV1 % predicted | 99.76 ± 12.22 | 94.29 ± 9.94 | < .001 |
| Postbronchodilator FVC, L | 3.67 ± 0.89 | 3.70 ± 0.94 | .67 |
| Postbronchodilator FVC % predicted | 98.45 ± 12.01 | 97.63 ± 10.56 | .44 |
| Prebronchodilator SVC, L | 3.61 ± 0.96 | 3.84 ± 1.05 | .016 |
| Postbronchodilator SVC, L | 3.68 ± 0.92 | 4.03 ± 0.99 | < .001 |
| Bronchodilator response | 86 (11.7) | 19 (15.8) | .26 |
| RVCT, L | 2.78 ± 0.72 | 3.15 ± 0.79 | < .001 |
| TLCCT, L | 5.38 ± 1.27 | 5.84 ± 1.33 | < .001 |
| RVCT to TLCCT ratio, % | 52.56 ± 11.96 | 54.94 ± 11.89 | .008 |
| 6-MWT distance, m | 440.52 ± 94.96 | 426.77 ± 95.93 | .30 |
| Emphysema, % | 1.53 ± 1.82 | 2.30 ± 2.25 | < .001 |
| Gas trapping, % | 7.58 ± 9.53 | 12.09 ± 12.08 | < .001 |
| PRMfSAD, % | 8.01 ± 9.74 | 12.73 ± 12.27 | < .001 |
Data are presented as No. (%) or mean ± SD, unless otherwise indicated. 6-MWT = 6-min walk test distance; CAT = COPD Assessment Test; MMRC= Modified Medical Research Council; PRMfSAD = parametric response mapping functional small airways disease; RVCT = residual volume by CT scan; SVC = slow vital capacity; TLCCT = total lung capacity by CT scan.
a
Normal spirometry results defined as postbronchodilator FEV1 of ≥ 80% and postbronchodilator FEV1/FVC ≥ 0.7.
b
Characteristics of participants between the two groups compared using a t test for continuous variable and the χ 2 or Fisher exact test for categorical variables.