Multivariate linear regression models, with% low-attenuation areas < -950 Hounsfield units (HU) and AWT-Pi10 as dependent variables in chronic obstructive pulmonary disease (COPD) cases and controls
| COPD cases | Controls | |||
| coefficient | p-value | coefficient | p-value | |
| % Low-attenuation areas < -950 HU# | ||||
| Subjects n | 462 | 428 | ||
| Intercept | -1.062±0.464 | <0.05 | -3.438±0.373 | <0.001 |
| Male | 0.272±0.130 | <0.05 | 0.674±0.113 | <0.001 |
| Age per 10 yrs | 0.397±0.070 | <0.001 | 0.450±0.065 | <0.001 |
| Pack-years per 10 pack-yrs | 0.085±0.039 | <0.05 | 0.011±0.048 | >0.05 |
| Smoking groups | <0.05 | >0.05 | ||
| Ex-smokers | 0 | 0 | ||
| Current | ||||
| <10 cigarettes·day−1 | -0.181±0.200 | >0.05 | -0.349±0.181 | >0.05 |
| 10–19.9 cigarettes·day−1 | -0.451±0.155 | <0.01 | -0.099±0.146 | >0.05 |
| ≥20 cigarettes·day−1 | -0.430±0.207 | <0.05 | -0.458±0.235 | >0.05 |
| Adjusted R2 | 0.1421 | 0.2159 | ||
| AWT-Pi10¶ | ||||
| Subjects n | 438 | 407 | ||
| Intercept | 0.497±0.011 | <0.001 | 0.472±0.009 | <0.001 |
| Male | 0.031±0.003 | <0.001 | 0.024±0.003 | <0.001 |
| Age per 10 yrs | -0.004±0.001 | <0.05 | -0.003±0.001 | <0.05 |
| Pack-years per 10 pack-yrs | -0.0002±0.0009 | >0.05 | 0.005±0.001 | <0.001 |
| Smoking groups | <0.01 | >0.05 | ||
| Ex-smokers | 0 | 0 | ||
| Current | ||||
| <10 cigarettes·day−1 | -0.011±0.005 | <0.05 | 0.002±0.004 | >0.05 |
| 10–19.9 cigarettes·day−1 | 0.007±0.004 | >0.05 | -0.007±0.003 | <0.05 |
| ≥20 cigarettes·day−1 | 0.005±0.005 | >0.05 | -0.001±0.005 | >0.05 |
| Adjusted R2 | 0.2121 | 0.2218 | ||
Data are presented as coefficient±se, unless otherwise stated. AWT-Pi10: airway wall thickness for an airway with an internal perimeter of 10 mm. #: log-transformed; ¶: standardised measure of airway wall thickness.