The joint effects of some beverages intake and smoking on chronic obstructive pulmonary disease in Korean adults: Data analysis of the Korea national health and nutrition examination survey (KNHANES), 2008-2015

Some beverages and smoking cause an inflammatory response in the lungs and airways in a similar way, ultimately affecting chronic obstructive pulmonary disease (COPD) occurrence. Using a nationally representative health survey database, this study investigates the individual and joint effects of consumption of different beverages and smoking on COPD. This study is a crosssectional analysis of 15,961 Korean adults in the Korea National Health and Nutritional Examination Survey of 2008-2015. COPD was defined as forced expiratory volume in 1 s (FEV₁) divided by forced vital capacity (FVC) <0.70. We used multiple linear and logistic regression models to examine the association of beverage consumption and smoking with an FEV₁/FVC ratio and odds ratio (OR) for COPD. The mean FEV₁/FVC ratio decreased with increasing soda intake (p = 0.016), coffee intake (p = 0.031), and smoking status; however, the mean FEV₁/FVC ratio increased with increasing green tea intake frequency (p = 0.029). When soda intake increased to 10 times/month, the OR of having COPD increased to 1.04 times (95% CI: 1.01, 1.07). The positive joint effect of soda intake and smoking on COPD was marginally significant (p = 0.058). We found that soda intake, coffee intake, and smoking increased airflow limitation while green tea intake decreased it. In addition, soda intake and smoking had a positive joint effect on COPD in the Korean population.