COPD Risk Factor Profiles in General Population and Referred Patients: Potential Etiotypes

Figures & data

Figure 1 Selection of study subjects from the KNHANES, a dataset of the general population (A), and from the KOLD, a dataset of referral clinics (B). *According to the original study design of the KNHANES, spirometry was performed in subjects 40 years or older only.

Abbreviations: COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 sec; FVC, forced vital capacity; KNHANES, Korea National Health and Nutrition Examination Survey; KOLD, Korean Obstructive Lung Disease cohort.

Table 1 Characteristics of Subjects Selected from the KNHANES, the Data of the General Population, and from the KOLD, the Data of Referral Clinics

	KNHANES			KOLD
	Sub-Total (n = 17,608)	Non-COPD Group (n = 15,178)	COPD Group (n = 2430)	*COPD Group (n = 579)
Male	7701 (43.7%)	5972 (39.3%)	1729 (71.2%)	543 (93.8%)
Age, years	58.4 ± 11.2	57.0 ± 10.9	66.6 ± 9.7	67.3 ± 8.0
BMI, kg/m^2	24.2 ± 3.2	24.3 ± 3.3	23.7 ± 2.9	23.1 ± 3.1
Pulmonary function test
FEV1/FVC ratio (%)	77.1 ± 7.4	79.2 ± 4.7	63.4 ± 6.8	46.2 ± 11.0
FEV1 (L)	2.6 ± 0.7	2.6 ± 0.7	2.2 ± 0.7	1.5 ± 0.6
FEV1% predicted	88.9 ± 13.6	91.0 ± 12.0	79.1 ± 16.1	55.4 ± 17.0
FVC (L)	3.3 ± 0.9	3.3 ± 0.8	3.4 ± 0.9	3.3 ± 0.8
FVC % predicted	89.0 ± 12.5	89.3 ± 12.0	86.6 ± 15.4	84.9 ± 17.2

Notes: Data are presented as mean ± standard deviation or number (%). We defined COPD by FEV₁/FVC ratio <0.7 in this study. *No subject was classified into the non-COPD group in the KOLD because all those enrolled had airway diseases of COPD, asthma, or both, according to the enrollment criteria of the original study design.

Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 sec; FVC, forced vital capacity; KNHANES, Korea National Health and Nutrition Examination Survey; KOLD, Korean Obstructive Lung Disease cohort.

Table 2 Risk Factors of Subjects in the COPD Groups from the KNHANES and the KOLD

	KNHANES COPD Group (n = 2430)	KOLD COPD Group (n = 579)
Risk factors
C (cigarette smoking)	1326 (54.6%)	512 (88.4%)
I (infection)	229 (9.4%)	154 (26.6%)
P (pollution)	259 (10.7%)	241 (41.6%)
A (asthma)	192 (7.9%)	204 (35.2%)
U (unidentified)	793 (32.6%)	18 (3.1%)
Number of risk factors among the above four
0*	793 (32.6%)	18 (3.1%)
1	1296 (53.3%)	178 (30.7%)
2	313 (12.9%)	231 (39.9%)
3	28 (1.2%)	137 (23.7%)
4	0 (0.0%)	15 (2.6%)
C only	1024 (42.1%)	157 (27.1%)
I only	86 (3.5%)	4 (0.7%)
P only	103 (4.2%)	7 (1.2%)
A only	83 (3.4%)	10 (1.7%)
C + I	97 (4.0%)	34 (5.9%)
C + P	115 (4.7%)	130 (22.5%)
C + A	63 (2.6%)	44 (7.6%)
I + P	11 (0.5%)	5 (0.9%)
I + A	14 (0.6%)	8 (1.4%)
P + A	13 (0.5%)	10 (1.7%)
C + I + P	9 (0.4%)	20 (3.5%)
C + I + A	11 (0.5%)	63 (10.9%)
C + P + A	7 (0.3%)	49 (8.5%)
I + P + A	1 (0.0%)	5 (0.9%)
C + I + P + A	0 (0.0%)	15 (2.6%)

Notes: Table compares the frequency of exposure to risk factors of subjects in the COPD groups from KNHANES (the data of the general population) and KOLD (the data of referral clinics). Data are presented as number (%). *Zero indicates that no risk was identified among the four risk factors of C, I, P, and A. Zero risk factors is the same as “Unidentified” in this study.

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; U, unidentified; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey; KOLD, Korean Obstructive Lung Disease cohort.

Figure 2 Profiles of risk factors in subjects with COPD from the KNHANES, a dataset of the general population (A) and from the KOLD, a dataset of referral clinics (B).

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey; KOLD, Korean Obstructive Lung Disease cohort.

Figure 3 Profile (A) and number (B) of risk factors in subjects with COPD from the KNHANES (general population) and from the KOLD (referral clinics).

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey; KOLD, Korean Obstructive Lung Disease cohort.

Table 3 Risk Factors of Subjects in the COPD and the Non-COPD Groups from the KNHANES

	Total (n = 17,608)	COPD Group (n = 2430)	Non-COPD Group (n = 15,178)	p-value
Risk factors
C (cigarette smoking)	5118 (29.1%)	1326 (54.6%)	3792 (25.0%)	<0.001
I (infection)	786 (4.5%)	229 (9.4%)	557 (3.7%)	<0.001
P (pollution)	1795 (10.2%)	259 (10.7%)	1536 (10.1%)	0.415
A (asthma)	465 (2.6%)	192 (7.9%)	273 (1.8%)	<0.001
U (unidentified)	10,425 (59.2%)	793 (32.6%)	9632 (63.5%)	<0.001
Number of risk factors among the above four				<0.001
0*	10,425 (59.2%)	793 (32.6%)	9632 (63.5%)
1	6247 (35.5%)	1296 (53.3%)	4951 (32.6%)
2	891 (5.1%)	313 (12.9%)	578 (3.8%)
3	45 (0.3%)	28 (1.2%)	17 (0.1%)
4	0 (0.0%)	0 (0.0%)	0 (0.0%)
C only	4312 (24.5%)	1024 (42.1%)	3288 (21.7%)	<0.001
I only	416 (2.4%)	86 (3.5%)	330 (2.2%)	<0.001
P only	1244 (7.1%)	103 (4.2%)	1141 (7.5%)	<0.001
A only	275 (1.6%)	83 (3.4%)	192 (1.3%)	<0.001
C + I	244 (1.4%)	97 (4.0%)	147 (1.0%)	<0.001
C + P	421 (2.4%)	115 (4.7%)	306 (2.0%)	<0.001
C + A	100 (0.6%)	63 (2.6%)	37 (0.2%)	<0.001
I + P	60 (0.3%)	11 (0.5%)	49 (0.3%)	0.308
I + A	29 (0.2%)	14 (0.6%)	15 (0.1%)	<0.001
P + A	37 (0.2%)	13 (0.5%)	24 (0.2%)	<0.001
C + I + P	21 (0.1%)	9 (0.4%)	12 (0.1%)	0.001
C + I + A	12 (0.1%)	11 (0.5%)	1 (0.0%)	<0.001
C + P + A	8 (0.0%)	7 (0.3%)	1 (0.0%)	<0.001
I + P + A	4 (0.0%)	1 (0.0%)	3 (0.0%)	0.448

Notes: Frequency of exposure to risk factors in subjects from the KNHANES (the data of a general population). We classified study subjects into two groups of COPD vs non-COPD. COPD was defined by an FEV₁/FVC ratio of <0.7. Additionally, we compared the difference in exposure to risk factors between the COPD and non-COPD groups. Data are presented as number (%). The variables were compared using the χ2 or Fisher’s exact test. *Zero indicates that no risk was identified among the four risk factors of C, I, P, and A. Zero risk factors are the same as “Unidentified” in this study.

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; U, unidentified; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey.

Table 4 Contribution of Each Risk Factor for COPD in the Male Subjects of the KNHANES

	Univariate Analysis		Multivariate Analysis
	Odds Ratio (95% CI)	p-value	Adjusted Odds Ratio (95% CI)	p-value
C (cigarette smoking)	1.92 (1.70–2.16)	<0.001	2.14 (1.88–2.45)	<0.001
I (infection)	2.10 (1.72–2.57)	<0.001	1.51 (1.20–1.90)	<0.001
P (pollution)	1.28 (1.06–1.54)	0.009	0.98 (0.80–1.20)	0.872
A (asthma)	6.32 (4.52–8.85)	<0.001	5.92 (3.97–8.85)	<0.001
Age	1.09 (1.09–1.10)	<0.001	1.09 (1.09–1.10)	<0.001
Body mass index	0.89 (0.87–0.91)	<0.001	0.92 (0.90–0.94)	<0.001

Notes: Using the KNHANES (data of the general population), univariate and multivariate analysis by logistic regression analysis was performed to evaluate the contributions of each risk factor for COPD. For adjustment, age and body mass index were included as covariates.

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; CI, confidence interval; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey.

Table 5 Contribution of Each Risk Factor for COPD in the Female Subjects of the KNHANES

	Univariate Analysis		Multivariate Analysis
	Odds Ratio (95% CI)	p-value	Adjusted Odds Ratio (95% CI)	p-value
C (cigarette smoking)	2.88 (2.09–3.97)	<0.001	2.99 (2.10–4.24)	<0.001
I (infection)	3.41 (2.58–4.50)	<0.001	2.76 (2.04–3.74)	<0.001
P (pollution)	1.11 (0.88–1.40)	0.375	0.96 (0.75–1.22)	0.709
A (asthma)	6.54 (5.08–8.43)	<0.001	5.13 (3.89–6.76)	<0.001
Age	1.09 (1.08–1.09)	<0.001	1.09 (1.08–1.10)	<0.001
Body mass index	0.96 (0.94–0.99)	0.001	0.92 (0.90–0.94)	<0.001

Notes: Using the KNHANES (data of the general population), univariate and multivariate analysis by logistic regression analysis was performed to evaluate the contributions of each risk factor for COPD. For adjustment, age and body mass index were included as covariates.

Abbreviations: C, cigarette smoking; I, infection; P, exposure to biomass or pollution; A, asthma; CI, confidence interval; COPD, chronic obstructive pulmonary disease; KNHANES, Korea National Health and Nutrition Examination Survey.