About 65 million people around the world find it distressingly difficult to breathe due to chronic obstructive pulmonary disease (COPD) (1). COPD is a major cause of morbidity and mortality worldwide (2) and is one of the ten leading causes of death in South Korea. The epidemiologic study carried out by the South Korean National Health and Nutritional Examination Survey (KNHANES) in 2008 showed that COPD prevalence in the population over the age of 40 was 19.4% among men and 7.9% among women, respectively (3).