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±2800.0115
FEV1 mL per year−40.0±61.5−35.9±50.00.0142
Loss of >300 mL in FEV1 n (%)570 (36.8%)1055 (32.19%)0.002
mMRC dyspnoea score#0.0575±1.430.0649±1.140.87
SGRQ total score0.0442±19.50.298±13.20.6
Distance walked feet−130±401−128±3350.82
Adjusted lung density+−1.90±12.1−0.35±11.50.0003
Emphysema+ %0.677±3.740.06±3.95<0.0001
Gas trapping§ %2.31±9.520.623±8.17<0.0001
Airway wall thickness mm−0.0061±0.137−0.0025±0.1080.409
 Current smokers−0.0051−0.0170.083
 Former smokers−0.00860.00510.0291

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).