| Summary: | Hye Jung Park,1 Min Kwang Byun,1 Hyung Jung Kim,1 Jae Yeol Kim,2 Yu-Il Kim,3 Kwang-Ha Yoo,4 Eun Mi Chun,5 Ji Ye Jung,6 Sang Haak Lee,7 Chul Min Ahn1 On behalf of the Korean Smoking Cessation Study Group 1Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, 2Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, 3Department of Internal Medicine, Chonnam National University Hospital, Gwangju, 4Department of Internal Medicine, Konkuk University School of Medicine, 5Department of Internal Medicine, Ewha Womans University School of Medicine, 6Division of Pulmonology, Department of Internal Medicine, Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, 7Division of Pulmonology, Critical Care and Sleep Medicine, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea Background: Vitamin C, as an antioxidant, has recently been suggested to provide protection against COPD; however, only few national cohort studies have investigated these effects. We aimed to confirm the protective effects of vitamin C against COPD in Korean patients. Patients and methods: We analyzed the data of 3,283 adults aged ≥40 years (representing 23,541,704 subjects) who underwent pulmonary function tests and responded to questionnaires on smoking history and vitamin C intake, with stratification variables and sampling weight designated by the Korea 2012 National Health and Nutrition Examination Survey. Results: Among all the subjects, 512 (representing 3,459,679 subjects; 15.6%) were diagnosed as having COPD based on pulmonary function test results. Male gender, old age, residence in suburban/rural regions, low household income, low educational level, an occupation in agriculture or fisheries, and heavy smoking were significantly associated with COPD. Low intake of nutrients, including potassium, vitamin A, carotene, retinol, and vitamin C, was significantly associated with COPD. The prevalence of COPD in heavy smokers with the lowest quartile (Q1, <48.50 mg; 63.0%) and low-middle quartile (Q2, 48.50-84.38 mg; 56.4%) of vitamin C intake was significantly higher than that in subjects with the high-middle quartile (Q3, 84.38-141.63 mg; 29.5%) and highest quartile (Q4, >141.63 mg; 32.6%) of vitamin C intake (P=0.015). In multivariate analysis, male gender, old age, heavy smoking, and a low intake of vitamin C were significant independent risk factors for COPD. A significant reduction of 76.7% in COPD risk was observed with a Q3 vitamin C intake compared to Q1 vitamin C intake (odds ratio, 0.233; 95% confidence interval, 0.094-0.576) in heavy smokers. Conclusion: This large-scale national study suggests that dietary vitamin C provides protection against COPD, independent of smoking history, in the general Korean population. Keywords: chronic obstructive lung disease, vitamin C, nutrition, risk factor, smoking
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