Chronic Obstructive Pulmonary Disease in Non-smokers: A Case-Comparison Study

Figures & data

Table 1.  Participant baseline characteristics

	Nonsmokers	Smokers
	Median (range)	Median (range)	p-value
n	48	45
Male (%)	40	49	NS
Age (years)	63 (47–83)	67 (46–87)	0.043
Height (cm)	165 (148–195)	168 (152–186)	NS
Weight (kg)	74.7 (48–143)	79.6 (52–112)	NS
Body mass index (kg/m^2)	27.6 (18.4–43.5)	26.8 (19.1–39.1)	NS
FEV1, post bronchodilator (% predicted)	53.4 (30.2–69.4)	42.2 (22.1–69.5)	<0.001
FVC, post bronchodilator (% predicted)	78.5 (35.1–113.6)	73.2 (33.6–112.8)	NS
FEV1/FVC ratio, postbronchodilator	0.55 (0.31–0.90)	0.50 (0.23–0.74)	0.036
GOLD stage	2 (2–3)	3 (2–4)	<0.001
GOLD stage II (%)	58.3	33.3
GOLD stage III (%)	41.7	44.4
GOLD stage IV (%)	0	22.2
Years since COPD diagnosis	16 (2–65)	10 (1–27)	0.064

Table 2.  Prevalence of asthma and allergy

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Diagnosis of asthma (%)	98	56	<0.001
Age of onset of asthma symptoms	16.1 (0–51)	35.7 (0–79)	<0.001
Asthma onset in childhood (%)	67	24	0.001
Years of asthma	46.7 (10–84)	31.4 (–13–76)	<0.001
Years of symptomatic asthma	45.1 (6–84)	25 (–9–59)	<0.001
Prolonged asthma remission (prevalence,%)	24	24	NS
Bronchodilator reversibility (prevalence,%)	47	48	NS
Relative change in FEV1 post bronchodilator (%)	17.9 (–19–55)	19.0 (–11–50)	NS
Exhaled nitric oxide (ppb)	33.5 (0–75)	19.3 (0–46)	<0.001
Eosinophil count (×10^9/L)	0.43 (0–1.22)	0.24 (0–0.60)	0.013
Personal history of other allergic disease (%)	19	9	NS
Family history of asthma or allergy (%)	52	38	NS
One or more positive skinprick tests (%)	85	53	0.003
Two or more positive skinprick tests (%)	62	29	0.004
Number of positive skinprick tests	2.1 (0–5)	1.0 (0–3.4)	<0.001
Taking inhaled corticosteroid (%)	94	91	NS
Symptomatic benefit from ICS (%)	55	24	0.021

Table 3.  Systemic inflammatory markers

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
C-reactive protein (mg/L)	5.4 (0–25.7)	5.6 (0–18.8)	NS
White cell count (×10^9/L)	7.3 (0–13.0)	7.4 (0–10.7)	NS
Neutrophil count (×10^9/L)	4.3 (0–9.3)	4.4 (0–7.3)	NS
Lymphocyte count (×10^9/L)	2.0 (0–3.2)	2.1 (0–3.4)	NS
Platelet count (×10^9/L)	274 (0–423)	268 (125–411)	NS
Alpha1 antitrypsin (g/L)	1.51 (0–2.13)	1.65 (1.01–2.29)	NS

Table 4.  Prevalence of family history of airways disease

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Family history of emphysema (%)	13	22	NS
Family history of chronic bronchitis (%)	13	9	NS
Family history of COPD (%)	22	31	NS
Family history of asthma (%)	41	31	NS
Family history of airways disease (%)	57	56	NS

Table 5.  Symptoms of respiratory disease

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Chronic cough, prevalence (%)	57	76	NS
Years with chronic cough	32.4 (0–74)	17.5 (0–48)	0.003
Chronic cough interferes with activities (%)	38	44	NS
Chronic sputum, prevalence (%)	49	58	NS
Years with chronic sputum	27.9 (0–74)	12.1 (0–36)	0.002
Chronic wheeze, prevalence (%)	45	36	NS
Years with wheeze	41.6 (0–85)	20.6 (0–61)	<0.001
Chronic dyspnoea, prevalence (%)	83	91	NS
Chronic severe dyspnoea, prevalence (%)	17	63	<0.001
Dyspnoea grade	2.5 (0–5)	3.8 (1–5)	0.002
Years with dyspnoea	34.3 (0–78)	13.2 (0–37)	<0.001
Number of positive responses to symptom questions	6.4 (0–14)	7.7 (1–14)	NS
URTIs in past 3 years	3.3 (0–7)	3.2 (0–7)	NS
LRTIs in past 3 years	2.8 (0–7)	2.8 (0–7)	NS
Number of medications for airways disease	3.0 (1–5)	3.3 (1–5)	NS

Table 6.  Other risk factors and environmental exposures

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Childhood domestic ETS exposure (prevalence,%)	68	89	0.027
Household ETS exposure, hours	22 005 (0–79 142)	49 929 (0–170 257)	0.007
Work ETS exposure, hours	6 217 (0–36 368)	33,226 (0–104 316)	<0.001
Other ETS exposure, hours	2 864 (0–18 417)	10 511 (0–50 356)	0.016
Total ETS exposure, hours	30 398 (0–102 468)	93 666 (0–267 164)	<0.001
Exposure to solid fuel smoke, cooking (%)	17	9	NS
Exposure to solid fuel smoke, heating (%)	9	5	NS
Cooking smoke exposure, years	19.1 (0–51)	36.9 (0–81)	NS
Heating smoke exposure, years	16.2 (4–29)	23.3 (23–23)	NS
Occupational dust and fume exposure (prevalence,%)	43	62	0.036
Years of exposure	9.6 (0–39)	17.5 (0–52)	0.048
Frequent childhood upperrespiratory tract infection (%)	44	21	0.026
Frequent childhood bronchitis (%)	45	19	0.008
Frequent childhood pneumonia (%)	14	2	NS
Pertussis (%)	17	31	NS

Table 7.  Static lung volumes and gas transfer

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Total lung capacity (% predicted)	104 (75–133)	115 (83–147)	0.008
Residual volume (% predicted)	126 (70–181)	153 (71–235)	0.003
RV/TLC ratio	0.46 (0.26–0.66)	0.51 (0.34–0.69)	0.078
Diffusion capacity for carbon monoxide (% predicted)	87 (52–121)	56 (22–91)	<0.001

Table 8.  Subjective scoring of HRCT scans

	Nonsmokers	Smokers
	Mean (95% CI)	Mean (95% CI)	p-value
Bronchiectasis prevalence (%)	40	50	NS
Number of bronchiectatic lobes*	0.9 (0–3.7)	1.1 (0–4.3)	NS
Severity score of bronchiectasis in worst-affected lobe	0.4 (0–1.5)	0.5 (0–1.4)	NS
Bronchial dilatation prevalence (%)	42	86	<0.001
Bronchial wall thickening prevalence (%)	87	12	<0.001
Large airway mucous pluggingprevalence (%)	19	7	0.067
Small airway mucous plugging prevalence (%)	8	88	<0.001
Emphysema prevalence (%)	0	33	<0.001
Emphysema extent (%)	0	4 (0–20)	0.002
Decreased attenuation prevalence (%)	86	33	<0.001
Decreased attenuation extent (%)	18 (0–48)	4 (0–20)	<0.001

*Only includes subjects with bronchiectasis in at least one lobe.