Table 3. Risk factors for COPD in all participants (n=3,223).

Risk factors	Odds ratio (95% CI)	P
Univariate analysis
Age (years)	1.1 (1.07–1.09)	<0.001
Male	4.1 (3.20–5.14)	<0.001
Smoking amount (pack-year)	1.1 (1.02–1.03)	<0.001
BMI	0.9 (0.86–0.93)	<0.001
Education status		<0.001
University	Reference
High school	1.0 (0.69–1.48)
Middle school	1.6 (1.08–2.35)
Elementary school	2.1 (1.49–2.88)
History of pulmonary tuberculosis	2.4 (1.73–3.39)	<0.001
Living below the poverty line	2.3 (1.87–2.91)	<0.001
Multivariate analysis
Age (years)	1.1 (1.06–1.09)	<0.001
Male	3.6 (2.64–4.89)	<0.001
Smoking amount (pack-year)	1.0 (1.00–1.01)	0.004
BMI	0.9 (0.89–0.97)	<0.001
History of pulmonary tuberculosis	1.8 (1.23–2.64)	0.002
Living below the poverty line	1.4 (1.08–1.82)	0.012

Multivariate logistic regression analysis using backward elimination was performed to evaluate the association between living below the poverty line and the prevalence of COPD, after adjusting for age, sex, smoking amount, BMI, education status, and the history of pulmonary tuberculosis. COPD, chronic obstructive pulmonary disease; BMI, body mass index.