title: Active and Passive Smoking and Serum Total Bilirubin in a Rural Korean Population.
abstract: BACKGROUND
  Serum bilirubin is an endogenous antioxidant biomarker and its low level is a potential risk factor for smoking related health disorders. This study investigated the association of cigarette smoke with serum total bilirubin among Koreans.
  
  
  METHODS
  Between 2006 and 2011, we examined 4899 Korean adults living in a rural community. After excluding 38 participants with serum bilirubin more than 2mg/dL, 75 participants who did not report their smoking status or who had liver or bile duct disorders, and 711 participants with liver enzymes exceeding the upper reference values, we performed a cross-sectional analysis on 4075 participants. Participants were classified into four groups: never-smokers without secondhand smoke exposure (SHSE), never-smokers with SHSE, former smokers, and active smokers. Serum total bilirubin concentration was measured using the enzyme method.
  
  
  RESULTS
  Compared to never-smokers without SHSE, never-smokers with SHSE (β = -0.025 mg/dL), former smokers (β = -0.049 mg/dL), and active smokers (β = -0.149 mg/dL) had significantly lower serum bilirubin even after adjusting for demographic factors, study year, alanine aminotransferase, gamma-glutamyl transferase, hemoglobin, lifestyle factors, and chronic diseases. A sex-stratified analysis indicated that for men, former smokers and active smokers were significantly associated with having lower bilirubin when compared to never-smokers without SHSE. However, for women, never-smokers with SHSE and active smokers were significantly associated with having lower bilirubin when compared to never-smokers without SHSE.
  
  
  CONCLUSIONS
  Our findings suggest that both active and passive cigarette smoking are associated with low serum bilirubin among Korean adults.
  
  
  CONCLUSIONS
  Our results suggest that not only active smoking but also passive smoking including SHSE can have an influence on decreasing serum bilirubin levels. With this different point of view, our study supports efforts to create smoke-free environments in order to foster more favorable serum bilirubin profiles, which may improve endothelial function and reduce the risk of cardiovascular disease.
authors.affiliation: Department of Public Health, Yonsei University Graduate School, Seoul, Republic of Korea;
authors.forename: Na Hyun
authors.initials: NH
authors.lastname: Kim
authors.affiliation: Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Cardiovascular and Metabolic Diseases Etiology Research Center, Yonsei University College of Medicine, Seoul, Republic of Korea hckim@yuhs.ac.
authors.forename: Hyeon Chang
authors.initials: HC
authors.lastname: Kim
authors.affiliation: Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea;
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea;
authors.forename: Ju-Mi
authors.initials: JM
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea;
authors.forename: Il
authors.initials: I
authors.lastname: Suh
mesh_terms: D000328:Adult; D000368:Aged; D001663:Bilirubin / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012424:Rural Population / Q000706:statistics & numerical data*; D012907:Smoking / Q000097:blood*; D014028:Tobacco Smoke Pollution / Q000032:analysis / Q000706:statistics & numerical data; D014029:Tobacco Use Disorder / Q000097:blood
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D001663:Bilirubin