Income status and 5-year change in spirometry, dyspnoea, health-related quality of life and imaging characteristics
| Low-income smokers (<USD 15 000 per year) | Higher-income smokers (>USD 15 000 per year) | p-value | |
| FEV1 % pred | −3.26±12.9 | −1.40±10.1 | <0.0001 |
| FEV1 mL | −225.6±342 | −202.1±280 | 0.0115 |
| FEV1 mL per year | −40.0±61.5 | −35.9±50.0 | 0.0142 |
| Loss of >300 mL in FEV1 n (%) | 570 (36.8%) | 1055 (32.19%) | 0.002 |
| mMRC dyspnoea score# | 0.0575±1.43 | 0.0649±1.14 | 0.87 |
| SGRQ total score | 0.0442±19.5 | 0.298±13.2 | 0.6 |
| Distance walked feet¶ | −130±401 | −128±335 | 0.82 |
| Adjusted lung density+ | −1.90±12.1 | −0.35±11.5 | 0.0003 |
| Emphysema+ % | 0.677±3.74 | 0.06±3.95 | <0.0001 |
| Gas trapping§ % | 2.31±9.52 | 0.623±8.17 | <0.0001 |
| Airway wall thickness mm | −0.0061±0.137 | −0.0025±0.108 | 0.409 |
| Current smokers | −0.0051 | −0.017 | 0.083 |
| Former smokers | −0.0086 | 0.0051 | 0.0291 |
Data are presented as mean±sd, unless otherwise stated. FEV1: forced expiratory volume in 1 s; mMRC: modified Medical Research Council; SGRQ: St George's Respiratory Questionnaire. #: n=1547 (low income), n=3271 (higher income); ¶: n=1503 (low income), n=3234 (higher income); +: n=1085 (low income), n=2489 (higher income); §: n=828 (low income), n=2133 (higher income).