| COPD subjects(n = 1888) | Smoker controls(n = 296) | Non-smoker controls(n = 201) | p Value† | |
| Age | 63.4 (7.2) | 54.7 (8.9) | 53.2 (8.6) | <0.001 |
| Male (%) | 1222 (65) | 161 (54) | 74 (37) | <0.001 |
| Smoking history (pack-years) | 49.2 (27.3) | 32.0 (22.1) | 0.4 (0.5) | <0.001 |
| Current smoker (%) | 746 (40) | 201 (68) | 0 | <0.001 |
| FEV1 (l) | 1.4 (0.5) | 3.4 (0.8) | 3.3 (0.8) | <0.001 |
| FEV1 (% pred) | 48.7 (15.5) | 108.6 (12.1) | 114.8 (14.0) | <0.001 |
| FEV1/FVC | 0.45 (0.11) | 0.79 (0.05) | 0.81 (0.05) | <0.001 |
| CT scans (n)* | 1496 | 260 | 165 | |
| % Low attenuation area (<−950 HU) | 16.9 (11.8) | 2.2 (2.9) | 3.9 (4.0) | <0.001 |
| CC-16 (ng/ml), median (IQR) | 4.9 (3.4) | 5.6 (3.1) | 6.4 (3.1) | <0.001 |
All values are number or mean and standard deviation (in brackets) unless otherwise stated.
The lung function measurements were performed following the administration of 180 μg salbutamol.
*CT scans is the number of CT scans available for qualitative analysis to assess the percentage of the lungs with a density of less than −950 HU.
†p values for difference between COPD subjects and smoker controls. All the parameters measured were significantly different between individuals with COPD and non-smoker controls (p<0.001).
CC-16, Clara cell secretory protein-16; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; IQR, interquartile range.