Symptoms, function and quality of life

Low-income smokers (<USD15000 per year)Higher-income smokers (>USD15000 per year)p-value
Phase 1
 Chronic bronchitis2214<0.0001
 mMRC score1.58±1.460.93±1.24<0.0001
 mMRC score >24928<0.0001
 Severe exacerbation within the past year137<0.0001
 SGRQ total31.74±23.319.3±18.8<0.0001
 6MWD feet1297±3811486±352<0.0001
 SF-36 PCS42.0±11.247.1±10.0<0.0001
 SF-36 MCS45.95±12.652.4±9.8<0.0001
Phase 2
 Chronic bronchitis2013<0.0001
 mMRC score >25231<0.0001
 Severe exacerbation within the past year147<0.0001
 SGRQ total31.79±23.119.6±19.0<0.0001
 6MWD feet1168±4381356±420<0.0001
 SF-36 PCS39.9±11.445.3±10.6<0.0001
 SF-36 MCS48.0±11.753.6±9.5<0.0001
 CAT score15.0±9.210.5±7.7<0.0001

Data are presented as % or mean±sd, unless otherwise stated. mMRC: modified Medical Research Council; SGRQ: St George's Respiratory Questionnaire; 6MWD: 6-min walking distance; SF-36: Medical Outcomes Study 36-item short-form questionnaire; PCS: physical component summary; MCS: mental component summary; CAT: Chronic Obstructive Pulmonary Disease Assesment Test.