TABLE 2.

Symptoms, function and quality of life

	Low-income smokers (<USD 15 000 per year)	Higher-income smokers (>USD 15 000 per year)	p-value
Phase 1
Chronic bronchitis	22	14	<0.0001
mMRC score	1.58±1.46	0.93±1.24	<0.0001
mMRC score >2	49	28	<0.0001
Severe exacerbation within the past year	13	7	<0.0001
SGRQ total	31.74±23.3	19.3±18.8	<0.0001
6MWD feet	1297±381	1486±352	<0.0001
SF-36 PCS	42.0±11.2	47.1±10.0	<0.0001
SF-36 MCS	45.95±12.6	52.4±9.8	<0.0001
Phase 2
Chronic bronchitis	20	13	<0.0001
mMRC	1.64±1.51	0.99±1.29	<0.0001
mMRC score >2	52	31	<0.0001
Severe exacerbation within the past year	14	7	<0.0001
SGRQ total	31.79±23.1	19.6±19.0	<0.0001
6MWD feet	1168±438	1356±420	<0.0001
SF-36 PCS	39.9±11.4	45.3±10.6	<0.0001
SF-36 MCS	48.0±11.7	53.6±9.5	<0.0001
CAT score	15.0±9.2	10.5±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.