Characteristics and Prevalence of Early Chronic Obstructive Pulmonary Disease in a Middle-Aged Population: Results from a Nationwide-Representative Sample

Figures & data

Figure 1 The prevalence of early chronic obstructive pulmonary disease in a middle-aged Korean population (A) and in smokers with ≥10 pack-years (B). Data are expressed as proportions or means with 95% confidence intervals (error bars).

Table 1 Characteristics of Study Participants Under 50 Years of Age According to the Presence of Early COPD

	Early COPD (n=69)	Control (n=3126)	P-value
Age	44.5 (43.8–45.3)	45.1 (45.0–45.3)	0.116
Men	92.7 (81.4–97.4)	49.6 (47.7–51.4)	<0.001
Residence			0.098
Urban	94.4 (85.8–97.9)	88.4 (85.1–91.0)
Rural	5.6 (2.1–14.2)	11.6 (9.0–14.9)
Household income			0.482
Lowest	2.5 (0.6–10.0)	6.3 (5.4–7.5)
Lower middle	22.3 (12.6–36.2)	20.7 (18.8–22.9)
Higher middle	41.0 (28.2–55.2)	33.8 (31.4–36.2)
Highest	34.1 (21.6–49.3)	39.2 (36.3–42.1)
Education			0.354
Middle school or lower	4.4 (1.1–16.6)	3.3 (2.6–4.2)
High school	47.5 (34.7–60.6)	38.2 (35.7–40.9)
College or more	48.1 (35.1–61.3)	58.5 (55.7–61.2)
Smoking status			<0.001
Never	–	55.6 (53.5–57.7)
Former	31.9 (20.4–46.1)	20.5 (18.7–22.3)
Current	68.1 (53.9–79.6)	23.9 (22.0–25.9)
Pack-years	21.8 (19.3–24.4)	15.0 (14.2–15.8)^¶	<0.001
Heavy alcohol consumption*			0.001
<1/wk	47.7 (34.6–61.0)	70.0 (67.9–72.0)
≥1/wk	52.3 (39.0–35.4)	30.0 (28.0–32.1)
BMI, kg/m^2	24.3 (23.5–25.1)	24.3 (24.2–24.5)	0.991
Lung function testing
FVC, L/s	4.51 (4.35–4.67)	3.07 (3.05–3.10)	<0.001
Predicted FVC%	94.6 (91.7–97.5)	92.2 (91.7–92.6)	0.094
FEV1, L/s	3.06 (2.94–3.18)	3.07 (3.05–3.10)	0.837
Predicted FEV1%	78.9 (75.8–82.1)	90.3 (89.8–90.7)	<0.001
FEV1/FVC%	67.7 (66.4–69.1)	80.4 (80.2–80.6)	<0.001
Quality of life
Chronic cough	3.1 (0.8–10.5)	1.6 (1.2–2.3)	0.341
Chronic sputum	8.1 (3.2–19.4)	2.3 (1.8–3.1)	0.006
EQ-5D index	0.99 (0.97–1.00)	0.98 (0.97–0.98)	0.363
Systolic blood pressure, mmHg	121.1 (117.4–124.9)	115.2 (114.6–115.9)	0.001
Diastolic blood pressure, mmHg	82.5 (79.8–85.1)	78.3 (77.8–78.7)	0.001
Laboratory findings
Fasting glucose, mg/dL	99.1 (96.4–101.8)	100.4 (99.4–101.4)	0.413
HbA1c, %	5.58 (5.48–5.67)	5.62 (5.58–5.65)	0.452
Triglyceride, mg/dL	196.0 (158.2–233.7)	155.4 (149.2–161.7)	0.003
LDL-cholesterol, mg/dL	130.9 (107.1–154.7)	119.1 (116.1–122.0)	0.309
HDL-cholesterol, mg/dL	49.9 (46.9–52.8)	51.0 (50.4–51.6)	0.457
Hematocrit, %	46.4 (45.3–47.4)	43.3 (43.1–43.5)	<0.001
HS-CRP, mg/dL	0.99 (0.73–1.25)	1.02 (0.96–1.09)	0.815
eGFR by MDRD, mL/min/1.73m^2	105.9 (101.9–109.9)	111.4 (110.4–112.4)	0.017
Urine cotinine, ng/mL	1291.6 (1018.5–1564.6)	426.6 (385.4–467.8)	<0.001
Urine NNAL, pg/mL	123.1 (74.4–171.8)	62.4 (52.4–72.4)	0.002

Notes: Data are presented as weighted numbers with 95% CI for continuous variables and weighted percentages with 95% CI for categorical variables, unless otherwise stated. Comparisons of numerical variables and categorical variables from complex sample surveys were performed using Student’s t-test and the chi-squared test of Fisher’s exact test, respectively. *Heavy alcohol consumption was defined as seven or more drinks for men and five or more drinks for women on one occasion. ^¶Pack-year in control group was calculated among former and current smokers.

Abbreviations: CI, confidence interval; BMI, body mass index; FVC, forced vital capacity; FEV₁, forced expiratory volume in one second; EQ-5D, European Quality of Life-5 Dimensions; LDL, low-density lipoprotein; HDL, high-density lipoprotein; HS-CRP, high sensitivity C-reactive protein; eGFR, estimated glomerular filtration rate; MDRD, modification of diet in renal disease; NNAL, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol.

Table 2 Factors Affecting Early COPD Among Middle-Aged (40–49 Years) Adults

	Univariate		Multivariate
	OR (95% CI)	P-value	OR (95% CI)	P-value
Men	12.95 (4.44–37.76)	<0.001	8.09 (2.58–25.36)	<0.001
Residence		0.107		0.093
Rural	1		1
Urban	2.20 (0.84–5.73)		2.37 (0.87–6.46)
Household income		0.450		0.594
Lowest	1		1
Lower middle	2.68 (0.56–12.80)	0.216	2.18 (0.41–11.64)	0.363
Higher middle	3.03 (0.69–13.31)	0.142	2.88 (0.58–14.29)	0.195
Highest	2.68 (0.56–12.80)	0.307	2.53 (0.51–12.50)	0.253
Education		0.327		0.148
Middle school or lower	1		1
High school	0.92 (0.21–4.15)	0.916	0.62 (0.13–2.94)	0.551
College or more	0.61 (0.13–2.79)	0.524	0.35 (0.07–1.74)	0.199
Heavy alcohol consumption*		0.001		0.158
<1/wk	1		1
≥1/wk	2.56 (1.47–4.46)		1.58 (0.84–2.97)
BMI		0.883		0.482
<23 kg/m^2	1		1
23–24.9 kg/m^2	1.08 (0.53–2.24)	0.828	0.91 (0.45–1.82)	0.781
≥25 kg/m^2	1.16 (0.65–2.07)	0.619	1.38 (0.74–2.56)	0.313
Chronic cough		0.349		0.803
No	1		1
Yes	1.91 (0.49–7.44)		1.22 (0.25–5.94)
Chronic sputum		0.011		0.097
No	1		1
Yes	3.70 (1.36–10.09)		2.37 (0.85–6.57)
Hypertension^¶		0.001		0.020
No	1		1
Yes	2.39 (1.45–3.96)		2.10 (1.12–3.91)
Fasting glucose, mg/dL		0.881		0.733
<100	1		1
≥100	1.41 (0.83–2.41)		1.16 (0.59–2.09)
HbA1c, %		0.472		0.410
<6.5	1		1
≥6.5	0.57 (0.12–2.67)		0.51 (0.10–2.57)
Triglyceride, mg/dL		0.003		0.063
<150	1		1
≥150	2.20 (1.31–3.72)		1.90 (0.97–3.76)
HDL-cholesterol, md/dL		0.140		0.167
≥40 (men) and ≥50 (women)	1		1
<40 (men) and <50 (women)	0.63 (0.34–1.17)		0.62 (0.32–1.22)
Waist circumference, cm		0.684		0.302
<90 (men) and <85 (women)	1		1
≥90 (men) and ≥85 (women)	0.89 (0.50–1.57)		0.63 (0.26–1.52)
eGFR by MDRD, mL/min/1.73m		0.045		NA
>60	1		1
≤60	9.27 (1.05–81.55)		NA

Notes: Multivariate model considered age, sex, BMI, alcohol consumption, smoking status, educational level, household income level, and residence as covariates. *Heavy alcohol consumption was defined as seven or more drinks for men and five or more drinks for women on one occasion. ^¶Hypertension was defined based on the eighth Joint National Committee Blood Pressure Guideline.