Table 5.

Multivariate models for respiratory symptoms among severe COPD cases in different countries

Respiratory symptoms	Korea vs Poland*		USA vs Poland**		USA vs Korea**
	OR with 95% CI	p-value	OR with 95% CI	p-value	OR with 95% CI	p-value
Chronic bronchitis	0.30 (0.18–0.52)	<0.0001	0.59 (0.39–0.90)	0.01	1.83 (1.05–3.17)	0.03
mMRC dyspnea	0.50 (0.38–0.66)	<0.0001	0.55 (0.44–0.68)	<0.0001	0.96 (0.76–1.21)	0.7
Attacks of wheezing	2.56 (1.48–4.42)	0.0008	1.75 (1.14–2.67)	0.01	0.62 (0.36–1.06)	0.08

Notes:

^*Korean COPD cases are considered the reference population (ie, OR <1 denotes “decreased” prevalence in Korean cases).

^**USA COPD cases are considered the reference population (ie, OR <1 denoted “decreased” prevalence in USA cases). Logistic regression models used country of origin as the dependent variable, with independent variables including all three respiratory symptoms as well as age, sex, pack-years of smoking, and post-bronchodilator FEV₁ (% predicted). mMRC dyspnea is expressed as OR per 1 unit change in mMRC scale.

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