Prevalence of chronic obstructive pulmonary disease in asymptomatic smokers

Figures & data

Table 1 Demographic data of smokers according to the presence of symptoms

n (%)	WOS 637 (21.50)	WS 2,324 (78.50)	P-value
Male, n (%)	306 (49.90)	1,160 (49.91)	0.401
Age, m (SD)	49.63 (11.33)	51.92 (10.48)	0.000
Height cm, m (SD)	163.04 (9.06)	163.06 (9.46)	0.972
Weight kg, m (SD)	71.01 (14.28)	71.29 (14.83)	0.776
FEV1 post-BD mL, m (SD)	2.97 (0.76)	2.80 (0.83)	0.000
FEV1 post % predicted, mean (SD)	98.98 (16.55)	94.49 (19.48)	0.000
FEV1/FVC post %, m (SD)	81.03 (7.63)	79.10 (10.24)	0.000
FVC post mL, m (SD)	3.66 (0.89)	3.53 (0.94)	0.000
FVC post % predicted, m (SD)	99.90 (15.36)	97.25 (16.05)	0.000
Smoking status
Former smoker, n (%)	120 (18.84)	452 (19.45)	0.377
Current smoker, n (%)	517 (81.16)	1,872 (80.55)	0.377
Years of smoking, m (SD)	27.53 (11.12)	28.79 (11.31)	0.019
Cigarettes/day, m (SD)	14.53 (9.88)	15.85 (10.60)	0.009
Pack-years, median (IQR)	17.00 (8–28)	19.50 (10–33)	0.012
Respiratory symptoms
Cough, n (%)	0	1,249 (53.74)	–
Phlegm, n (%)	0	1,417 (60.97)	–
Wheezing, n (%)	0	137 (5.89)	–
Dyspnea, n (%)	0	1,611 (69.32)	–
At least one symptom, n (%)	0	2,324 (100)	–
COPD prevalence according to fixed GOLD ratio	45 (7.06)	284 (12.22)	0.000
COPD prevalence according to LLN	36 (5.65)	264 (11.35)	0.000

Note: Data is presented as either n (%), mean ± SD, or median IQR, χ² test, Student’s t-test, Mann–Whitney test were used as appropriate.

Abbreviations: BD, bronchodilator; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; IQR, interquartile range; LLN, lower limit of normal; m, mean; SD, standard deviation; WOS, smokers without symptoms; WS, smokers with symptoms.

Table 2 Demographic data of COPD patients according to the presence of symptoms

n (%)	Total 329 (100)	WOS 45 (13.7)	WS 284 (86.3)	P-value
Male, n (%)	195 (59.30)	25 (55.55)	170 (59.85)	0.585
Age, m (SD)	59.47±10.19	56.91 (9.78)	59.86 (10.22)	0.070
Height cm, m (SD)	164.19±9.46	166.09 (8.97)	163.79 (9.54)	0.212
Weight kg, m (SD)	70.53±16.08	67.95 (14.77)	71.01 (16.33)	0.415
FEV1 post-BD mL, m (SD)	1,969±810	2.20 (0.75)	1.93 (0.81)	0.036
FEV1 post-BD % predicted, m (SD)	68.92±26.95	78.52 (22.59)	67.42 (22.39)	0.002
FEV1/FVC post-BD, m (SD)	58.84±11.00	63.59 (11.45)	58.09 (11.55)	0.003
FVC post-BD mL, m (SD)	3,248±1,050	3.48 (1.01)	3.21 (1.05)	0.099
FVC post % predicted, m (SD)	89.26±20.97	94.25 (22.35)	88.46 (20.68)	0.093
Smoking status	Total
Former smoker, n (%)	64 (19.45)	7 (15.56)	57 (20.07)	0.353
Current smoker, n (%)	265 (80.55)	38 (84.44)	227 (79.93)	0.353
Years smoking, m (SD)	37.83 (11.91)	36.04 (10.67)	38.10 (12.09)	0.305
Cigarettes/day, m (SD)	20.13 (13.12)	16.92 (12.04)	20.60 (13.23)	0.102
Pack-years, median (IQR)	34.75 (18.71–51.00)	23 (13.25–37.00)	36.75 (20.00–53.00)	0.013
Respiratory symptoms
Cough, n (%)	165 (50.15)	–	165 (58.09)	–
Phlegm, n (%)	168 (52.66)	–	168 (59.15)	–
Wheezing, n (%)	137 (42.94)	–	137 (48.23)	–
Dyspnea, n (%)	224 (70.21)	–	224 (78.87)	–
COPD severity (GOLD)
I–II, n (%)	279 (84.80)	31 (68.88)	248 (87.32)	0.000
III–IV, n (%)	50 (15.20)	14 (31.12)	36 (12.68)	0.296

Note: Data is presented as either n (%), mean ± SD, or median IQR, χ² test, Student’s t-test, Mann–Whitney test were used as appropriate.

Abbreviations: BD, bronchodilator; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Obstructive Lung Disease; IQR, interquartile range; m, mean; SD, standard deviation; WOS, smokers without symptoms; WS, smokers with symptoms.

Table 3 Factors associated with COPD in asymptomatic subjects (univariate analysis)

Variable	OR	95% CI	P-value
Sex*	0.838	0.444–1.580	0.585
Current smoker	1.534	0.061–3.812	0.356
Cigarettes/day	0.975	0.945–1.005	0.103
FEV1, mL	1.485	1.021–2.159	0.038
Age, years	1.002	0.976–1.029	0.833
Pack-years	0.988	0.974–1.002	0.101
Height, cm	1.025	0.985–1.067	0.213
Weight, kg	0.987	0.957–0.017	0.413

Note:

* Reference category: female.

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; OR, odds ratio.

Table 4 Factors associated with COPD in asymptomatic subjects (multivariate analysis)

Variables	OR	95% CI	P-value
FEV1, mL	2.05	1.22–3.40	0.006
Sex 1= male	0.64	0.29–1.42	0.259
Smoking index, pack-years	0.99	0.97–1.00	0.099

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; OR, odds ratio.