Characteristics of Current Smokers versus Former Smokers with COPD and Their Associations with Smoking Cessation Within 4.5 Years: Results from COSYCONET

Figures & data

Figure 1 Flow chart of study population. Grey boxes indicate the study populations.

Table 1 Patient Characteristics at Visit 1

Variable	All Patients n = 2500	Ex-Smokers n = 1840	Current Smokers n= 660	p value
Age (y)	64.8 ± 8.5	66.0 ± 8.4	61.5 ± 8.0	<0.001
Height (cm)	170.9 ± 9.0	171.0 ± 8.9	170.5 ± 9.4	0.194
Sex (m/f) (%)	1520/980 (60.8/39.2%)	1159/681 (63.0/37.0%)	361/299 (54.7/45.3%)	<0.001
BMI (kg/m^2)	27.1 ± 5.4	27.4 ± 5.3	26.3 ± 5.7	<0.001
Years of smoking (y)	37.4 ± 12.1	34.9 ± 12.5	44.2 ± 7.8	<0.001
Pack-years	56.3 ± 36.5	59.3 ± 38.2	42.8 ± 23.7	<0.001
Age at smoking initiation (y)	17.7 ± 4.4	17.9 ± 4.3	17.4 ± 4.7	0.013
FEV1% predicted	56.3 ± 21.0	55.2 ± 21.2	59.4 ± 19.9	<0.001
FVC % predicted	78.6 ± 19.0	77.7 ± 19.2	81.1 ± 18.4	<0.001
FEV1/FVC	0.548 ± 0.137	0.542 ± 0.139	0.567 ± 0.129	<0.001
FRC % predicted	145.2 ± 37.6	144.3 ± 39.0	147.7 ± 33.2	0.002
RV % predicted	167.7 ± 53.2	167.0 ± 54.9	169.4 ± 48.4	0.024
TLCO % predicted	58.3 ± 22.2	58.5 ± 22.8	58.0 ± 20.5	0.747
KCO % predicted	65.2 ± 23.0	66.5 ± 23.6	61.6 ± 20.8	<0.001
ABI	1.18 ± 0.15	1.19 ± 0.14	1.17 ± 0.15	0.005
6MWD (% predicted)	65.6 ± 16.4	65.2 ± 16.8	66.4 ± 15.4	0.230
Cardiac disease	522 (20.9%)	394 (21.4%)	128 (19.4%)	0.289
Asthma	421 (16.8%)	322 (17.5%)	99 (15.0%)	0.146
CAT score	18.0 ± 7.4	18.0 ± 7.3	18.2 ± 7.4	0.504
SGRQ Total	42.9 ± 20.1	43.6 ± 20.2	40.9 ± 19.7	0.004
Activity	57.2 ± 26.2	59.4 ± 26.1	51.0 ± 25.5	<0.001
Impact	30.0 ± 20.8	30.5 ± 21.1	28.7 ± 19.9	0.098
Symptoms	55.4 ± 21.3	54.0 ± 21.1	59.1 ± 21.4	<0.001
GOLD grades 0–4	363/191/887/824/235 14.5/7.6/35.5/33.0/9.4%	266/129/612/634/199 14.5/7.0/33.3/34.5/10.8%	97/62/275/190/36 14.7/9.4/41.7/28.8/5.5%	<0.001
GOLD group A/B/E	1005/602/884 40.3/24.2/35.5%	692/458/685 37.7/25.0/37.3%	313/144/199 47.7/22.0/30.3%	<0.001

Notes: P values refer to the comparison of the smoker and ex-smoker groups using the Mann–Whitney-U-test. Mean values and standard deviations or numbers and percentages are given.

Abbreviations: BMI, body-mass index; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; FRC, functional residual capacity; RV, residual volume; TLCO, carbon monoxide transfer factor; KCO, transfer factor coefficient (ratio of TLCO to alveolar volume); ABI, ankle-brachial index; 6MWD, 6-minute walking distance; CAT, COPD Assessment Test; SGRQ, Saint George’s Respiratory Questionnaire; GOLD, Global Initiative for Chronic Obstructive Lung Disease; cardiac disease comprises cardiac failure and coronary artery disease.

Table 2 Patient Characteristics at Visit 1 of the Longitudinal Cohort with Follow-Up Until Visit 5

	Permanent Ex-Smokers n = 713	Permanent Smokers n = 175	Incident Ex-Smokers n = 55	p value
Age (y)	64.8 ± 8.0 *,**	59.8 ± 7.7	60.8 ± 7.3	<0.001
Height (cm)	171.3 ± 8.7	170.9 ± 9.9	171.8 ± 7.6	0.884
Sex (m/f)	437/276 (61.3/38.7%)	95/80 (54.3/45.7%)	29/26 (52.7/47.3%)	0.137
BMI (kg/m^2)	27.4 ± 5.1	26.9 ± 5.2	26.1 ± 5.0	0.114
Years of smoking (y)	34.0 ± 11.9 *,**	42.8 ± 7.8	43.1 ± 6.4	<0.001
Pack-years	59.5 ± 38.2 *,**	43.1 ± 20.2	35.7 ± 20.0	<0.001
Age at smoking initiation (y)	17.8 ± 4.1 *	17.0 ± 4.1	17.7 ± 4.4	0.014
FEV1% predicted	60.1 ± 20.0	67.6 ± 17.9 *,***	57.0 ± 20.0	<0.001
FVC % predicted	82.4 ± 17.6	87.1 ± 16.7 *	82.1 ± 19.2	0.011
FEV1/FVC	0.560 ± 0.129	0.608 ± 0.122 *,***	0.535 ± 0.114	<0.001
FRC % predicted	138.5 ± 34.4	140.2 ± 28.6	160.7 ± 33.2 **,***	<0.001
RV % predicted	159.3 ± 48.3	159.2 ± 42.6	184.9 ± 47.3 **,***	<0.001
TLCO % predicted	62.8 ± 22.0	65.2 ± 20.6	61.3 ± 17.3	0.113
KCO % predicted	69.8 ± 22.9	68.0 ± 22.1	64.5 ± 15.9	0.168
ABI	1.20 ± 0.14	1.18 ± 0.14	1.20 ± 0.12	0.594
6MWD (% predicted)	69.6 ± 14.4	71.0 ± 15.3	70.0 ± 11.9	0.543
Cardiac disease	134 (18.8%)	27 (15.4%)	10 (18.2%)	0.585
Asthma	135 (18.9%)	14 (8.0%)	14 (25.5%)	0.001
CAT total score	16.9 ± 7.0	17.4 ± 6.9	17.7 ± 7.4	0.602
SGRQ Total	38.6 ± 18.7	37.2 ± 18.4	38.5 ± 21.1	0.680
Activity	53.0 ± 25.5 *	44.1 ± 24.9	48.5 ± 25.7	<0.001
Impact	25.6 ± 18.8	26.1 ± 19.1	26.2 ± 20.8	0.959
Symptoms	51.7 ± 20.8 *	57.8 ± 19.7	57.2 ± 23.8	0.001
GOLD grade 0–4	107/73/284/211/38 15.0/10.2/39.8/29.6/5.3%	33/25/87/28/2 18.9/14.3/49.7/16.0/1.1%	3/6/26/17/3 5.5/10.9/47.3/30.9/5.5%	0.001
GOLD group A/B/E	330/151/232 46.3/21.2/32.5%	98/33/43 56.3/19.0/24.7%	31/11/13 56.4/20.0/23.6%	0.105

Notes: P values refer to the comparison of the three groups using the Kruskal–Wallis-test, with Bonferroni-adjusted post hoc comparisons at an overall significance level of 0.05 (* permanent ex-smokers vs permanent smokers, ** permanent ex-smokers vs incident ex-smokers, *** permanent smokers vs incident ex-smokers). Mean values and standard deviations or numbers and percentages are given.

Abbreviations: BMI, body-mass index; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; FRC, functional residual capacity; RV, residual volume; TLCO, carbon monoxide transfer factor; KCO, transfer factor coefficient (ratio of TLCO to alveolar volume); ABI, ankle-brachial index; 6MWD, 6-minute walking distance; CAT, COPD Assessment Test; SGRQ, Saint George’s Respiratory Questionnaire; GOLD, Global Initiative for Chronic Obstructive Lung Disease; cardiac disease comprises cardiac failure and coronary artery disease.

Figure 2 (A) Time course of FEV₁% predicted in permanent ex-smokers, permanent smokers and incident ex-smokers over visits 1 to 5. (B) Time course of FRC % predicted in permanent ex-smokers, permanent smokers and incident ex-smokers over visits 1 to 5. Mean values and 95% confidence intervals are shown. Only patients remaining in the study until visit 5 were included in this graph.

Figure 3 Variables associated with smoking cessation within the follow-up period of 4.5 y. Only patients who were smokers at visit 1 were included, and odds ratios and their 95% % confidence intervals are given for the various predictors at visit 1. BMI = body mass index, FEV₁ = forced expiratory volume in 1 s, FRC = functional residual capacity, RV = residual volume, TLCO = diffusing capacity of the lung for carbon monoxide. The odds ratios refer to characteristics of patients at visit 1 in terms of the number of units as indicated and relative to the mean of the whole study population.