The effects of secondhand smoke on chronic obstructive pulmonary disease in nonsmoking Korean adults

Background/Aims: Smoking is widely acknowledged as the single most important risk factor for chronic obstructive pulmonary disease (COPD). However, the risk of COPD in nonsmokers exposed to secondhand smoke remains controversial. In this study, we investigated the association of secondhand smoke exposure with COPD prevalence in nonsmokers who reported never smoking. Methods: This study was based on data obtained from the Korean National Health and Nutrition Examination Surveys (KNHANES) conducted from 2008 to 2010. Using nationwide stratified random sampling, 8,596 participants aged ${\geq}40$ years of age with available spirometry results were recruited. After selecting participants who never smoked, the duration of exposure to secondhand smoke was assessed based on the KNHANES questionnaire. Results: The prevalence of COPD was 6.67% in participants who never smoked. We divided the participants who had never smoked into those with or without exposure to secondhand smoke. The group exposed to secondhand smoke was younger with less history of asthma and tuberculosis, higher income, and higher educational status. Multivariate logistic regression analysis determined that secondhand smoke did not increase the prevalence of COPD. Conclusions: There was no significant difference in the prevalence of COPD between participants who had never smoked with or without exposure to secondhand smoke in our study. Thus, secondhand smoke may not be an important risk factor for the development of COPD in patients who have never smoked.