Clinical Characteristics of Non-Smoking Chronic Obstructive Pulmonary Disease Patients: Findings from the KOCOSS Cohort

Figures & data

Table 1. General characteristics of non-smoking COPD and smoking COPD.

Subjects n	Overall (N = 2477)	Non-smoking (N = 200, 8.1%)	Smoking (N = 2277, 91.9%)	p-value
Age, years	69.2 ± 8.0	68.5 ± 9.2	69.2 ± 7.9	0.30
Sex (Male)	2268 (92.3%)	85 (42.5%)	2183 (96.7%)	< 0.01
BMI (kg/m^2)	23.0 ± 3.3	23.8 ± 3.6	22.9 ± 3.3	<0.01
Education (>9years)	1106 (45.2%)	75 (38.1%)	1031 (45.8%)	0.04
Urban	1981 (80.9%)	162 (81.0%)	1819 (80.8%)	1.00
Tobacco exposure (pack-year)			42.6 ± 25.5
Biomass exposure (Y/N)	1786 (75.8%)	160 (81.6%)	1626 (75.2%)	0.06
Biomass exposure (years)	8.9 ± 12.4	10.6 ± 13.9	8.8 ± 12.3	0.08
Inhaler use	1983 (80.61)	161 (80.5%)	1822 (80.0%)	0.94
LAMA	565 (22.8%)	45 (22.5%)	520 (22.8%)	0.98
LABA	154 (6.2%)	9 (4.5%)	145 (6.4%)	0.37
LABA/LAMA	259 (10.5%)	19 (9.5%)	240 (10.5%)	0.73
ICS/LABA	319 (12.9%)	35 (17.5%)	284 (12.5%)	0.054
ICS/LABA/ LAMA	610 (24.6%)	49 (24.5%)	561 (24.6%)	1.00
Comorbidities
Diabetes mellitus	418 (16.9%)	24 (12.1%)	394 (17.4%)	0.07
Hypertension	974 (39.5%)	92 (46.7%)	882 (38.9%)	0.04
Osteoporosis	100 (4.1%)	21 (10.6%)	79 (3.5%)	<0.01
Gastroesophageal reflux disease	230 (9.3%)	28 (14.1%)	202 (8.9%)	0.02
Depression (BDI > 18)	146 (12.5%)	15 (19.5%)	131 (12.0%)	0.08
History of respiratory and allergic diseases
Bronchiectasis	180 (7.4%)	30 (15.5%)	150 (6.7%)	<0.01
TB	615 (25.0%)	72 (36.7%)	543 (24.0%)	<0.01
Respiratory infection in childhood	473 (19.6%)	57 (28.9%)	416 (18.7%)	<0.01
Asthma	793 (32.3%)	93 (47.4%)	700 (31.0%)	<0.01

Data are presented as n (%) or mean ± SD, unless otherwise stated.

# BDI: Beck Depression Inventory; 0–9 indicates minimal depression, 10–18 indicates mild depression, 19–29 indicates moderate depression, 30–63 indicates severe depression.

BMI Body mass index,LAMA long-acting muscarinic antagonist, LABA long-acting beta2-agonist, ICS inhaled corticosteroids.

Table 2. Difference of COPD exacerbation in non-smoking and smoking COPD.

	Non-smoking (N = 108)	Smoking (N = 1108)	Total (N = 1216)	p-value
Moderate to severe exacerbation	0.6 ± 1.5	0.5 ± 1.3	0.5 ± 1.4	0.66
Severe exacerbation	0.2 ± 0.7	0.1 ± 0.5	0.1 ± 0.5	0.28
Applying MV during hospitalisation	2 (1.9%)	13 (1.2%)	15 (1.2%)	0.87

MV mechanical ventilation.

Table 3. Differences in the risk of exacerbations between non-smoking COPD and smoking COPD.

	Moderate-to-severe exacerbation			Severe exacerbation
	OR	95%CI	p-value	OR	95%CI	p-value
Smoking	1.37	0.67–2.78	0.34	0.62	0.25–1.57	0.28
Age	1.01	0.99–1.04	0.18	1.02	0.99–1.05	0.17
Sex (male)	1.06	0.50–2.19	0.88	2.26	0.80–6.62	0.11
BMI	1.03	0.98–1.09	0.16	0.99	0.92–1.06	0.81
Previous exacerbation	2.82	2.04–3.93	<0.01	2.62	1.68–4.10	<0.01
FEV1	0.54	0.31–0.60	<0.01	0.18	0.10–0.29	<0.01

BMI body mass index; FEV₁ forced expiratory volume in 1 s.

Table 4. Differences of symptoms between non-smoking and smoking COPD patients.

	Non-smoking (N = 200)	Smoking (N = 2277)	P-value
Chronic bronchitis symptoms	23 (11.5%)	236 (10.4%)	0.73
mMRC score	1.4 ± 1.0	1.4 ± 0.9	0.87
SGRQ score	33.3 ± 19.8	33.8 ± 19.1	0.75
CAT score	15.2 ± 8.6	14.7 ± 7.9	0.40
6MWT, metres	380.3 ± 98.7	383.9 ± 119.6	0.67

Data are presented as n (%) or mean ± SD, unless otherwise stated.

mMRC modified Medical Research Council, SGRQ-C St. George’s Respiratory Questionnaire for COPD, CAT COPD Assessment Test, 6MWT 6-minute walk distance test.

Table 5. Comparisons of radiologic features between non-smoking and smoking COPD patients.

	Non-smoking (N = 200)	Smoking (N = 2277)	p-value
Chest X-ray Result			0.06
Abnormal	131 (74.9%)	1327 (67.5%)
Normal	44 (25.1%)	638 (32.5%)
Emphysematous change	19 (13.7%)	533 (30.1%)	<0.01
TB destroyed lung	16 (11.5%)	104 (5.9%)	0.01
Airway wall thickening	6 (4.3%)	49 (2.8%)	0.43
Bronchiectasis	21 (15.1%)	94 (5.1%)	<0.01
Chest CT Result
Abnormal	109 (96.5%)	1132 (91.9%)	0.12
Normal	4 (3.5%)	100 (8.1%)
Emphysematous change	13 (18.1%)	521 (56.9%)	<0.01
TB destroyed lung	9 (12.5%)	59 (6.4%)	0.09
Airway wall thickening	12 (16.7%)	110 (12.0%)	0.33
Bronchiectasis	21 (29.2%)	114 (12.5%)	<0.01

TB Tuberculosis, CT Computed Tomography.

Figure 1. Difference of FEV₁ decline between smoking and non-smoking COPD.

FEV1 Forced expiratory volume in 1 second, COPD Chronic obstructive pulmonary disease.

Table 6. Differences of lung function between non-smoking and smoking COPD patients.

Subjects n	Non-smoking (N = 200)	Smoking (N = 2277)	P-value
FEV1 (absolute, L)	1.43 ± 0.52	1.70 ± 0.60	<0.01
FEV1 (% predicted)	63.4 ± 21.6	61.7 ± 19.2	0.31
FVC (absolute, L)	2.56 ± 0.81	3.33 ± 0.79	<0.01
FVC (% predicted)	80.7 ± 18.9	85.3 ± 18.1	<0.01
FEV1/FVC (%)	55.9 ± 11.0	50.7 ± 12.5	<0.01
DLCO, % predicted	76.1 ± 21.7	72.9 ± 23.2	0.12
RV/TLC (%)	45.0 ± 14.3	44.0 ± 14.1	0.46

FEV1 Forced expiratory volume in 1 s, FVC Forced vital capacity, DLCO Diffusion capacity of carbon monoxide, RV Residual volume, TLC Total lung capacity.

Data availability statement

The datasets supporting the conclusions of this article are available from the corresponding author on reasonable request.