Chronic obstructive pulmonary disease (COPD) is characterized by persistent and progressive airflow limitation¹. COPD has emerged as a serious public health concern in recent years, and is predicted to become the fourth leading cause of death worldwide by 2030^1,2.

The worldwide prevalence of COPD has been estimated to be 7.5%-10%³. In a nationwide COPD prevalence survey in Korea in conjunction with the second Korea National Health and Nutrition Examination Survey (KNHANES II) conducted 2001, 17.2% of Korean adults over the age of 45 years had COPD⁴. And, follow-up studies reported in 2011 showed the prevalence of COPD was 13.4% and 12.9%^5,6.

There were a few studies about the change of the prevalence of COPD, which showed the prevalence of COPD did not increase^7,8.

In this article, we briefly review the trends in the prevalence of COPD in Korea from 2007 to 2015 using the data from KNHANES⁹.

KNHANES is an ongoing surveillance system in the Republic of Korea that assesses the health and nutritional status of Koreans, monitors trends in health risk factors and the prevalence of major chronic diseases, and provides data for the development and evaluation of health policies and programs in Korea. KNHANES was initiated in 1998 by the union of “National Nutrition Survey” and the “National Health and Health Behavior Survey.” Since then, surveys for the KNHANES I, II, III, IV, V, and VI have been executed. The first three KNHANES were conducted as a triannual survey. To reduce the limitation of seasonal variations, beginning with the fourth KNHANES in 2007, it was converted to an annual survey to provide timely national statistics. The survey for the KNHANES VII is under progress since 2016. The KNHANES uses rolling sampling survey method for the sample in each year to present the whole nation and to be similar by years. Twenty households were selected throughout 192 regions each year and 10,000 individuals aged 1 year and over were targeted for KNHANES⁹.

In KNHANES, spirometry was performed by four technicians, each of whom underwent education sessions on pulmonary function test (PFT) and quality control^5,6. Spirometry was performed using dry rolling seal spirometers (Model 2130; SensorMedics, Yorba Linda, CA, USA) and the American Thoracic Society/European Respiratory Society criteria for the standardization of PFT¹⁰. The prediction equation used in KNHANES was derived from the KNHANES II¹¹. The results of spirometry in each enumeration districts were stored on web-hard to investigate whether the results satisfied acceptability and reproducibility criteria of spirometry for quality control and quality assurance. For analysis on results of spirometry, only results showing two or more acceptable curves and meeting reproducibility criteria were used⁶.

Also, trained interviewers administered the questionnaire at the time of spirometry, to determine whether (1) the subject had a history of COPD, such as chronic bronchitis or emphysema; (2) had been diagnosed with COPD by a physician; and (3) had been treated for COPD⁹.

The participants aged over 40 years recording less than 0.7 of forced expiratory volume in 1 second (FEV₁)/forced vital capacity (FVC) were defined to have COPD^5,6. To explore the trends of COPD prevalence from 2007 to 2015, KNHANES used age-standardized prevalence which was calculated using the age- and sex-specific structures of estimated population based on the 2005 Korea Census⁹.

The prevalence of COPD among Korean adults aged over 40 years was 13.4% in 2015. The prevalence of COPD did not change significantly during the period from 2010 to 2015. And most COPD patients still had not been diagnosed by physicians and consequently had not been treated appropriately.