Demographics and baseline disease severity
| Low-income smokers (<USD 15 000 per year) | Higher-income smokers (>USD 15 000 per year) | p-value | |
| Subjects n | 1549 | 3277 | |
| Age years | 55.7±7.4 | 61.7±8.5) | <0.0001 |
| African American | 57 | 16 | <0.0001 |
| Male | 49 | 52 | 0.031 |
| BMI kg·m−2 | 29.1±6.7 | 29.1±5.7 | 0.95 |
| More than high-school education | 45 | 77 | <0.0001 |
| ATS pack-years | 42.5±25.0 | 42.2±22.6 | 0.66 |
| Age started smoking years | 16.7±5.1 | 17.2±4.1 | 0.0016 |
| Current smoking status | 73 | 36 | <0.0001 |
| Using respiratory medications | 42 | 31 | <0.0001 |
| FEV1 % pred | 78.4±23.2 | 80.4±23.0 | 0.0042 |
| FVC % pred | 87.7±17.8 | 89.6±16.5 | 0.0002 |
| FEV1/FVC | 0.70±0.14 | 0.68±0.14 | 0.0003 |
| Percentage emphysema LAA@-950 HU | 4.68±7.6 | 6.24±8.9 | <0.0001 |
| Percentage gas trapping LAA@-856 HU | 19.3±17.9 | 20.5±17.8 | 0.0652 |
| Airway wall thickness mm | 1.063±0.231 | 1.018±0.211 | <0.0001 |
Data are presented as mean±sd or %, unless otherwise stated. BMI: body mass index; ATS: American Thoracic Society; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LAA: low-attenuation areas.