Association of serum bilirubin level with lung function decline: a Korean community-based cohort study

BACKGROUND: Bilirubin has been reported to be associated with respiratory diseases due to its antioxidant action. We aimed to evaluate the relationship between serum bilirubin concentration and annual lung function decline in the Korean general population. METHODS: The study included 7986 subjects aged 40–69 years from the Ansung-Ansan cohort database I (2001–2002)–III (2005–2006). We analyzed the relationships between serum bilirubin level and forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), FEV(1)/FVC, and mean forced expiratory flow between 25 and 75% of FVC (FEF(25–75%)) at baseline, as well as the annual average changes in these lung parameters. RESULTS: The FEV(1), FVC, and FEF(25–75%) were significantly associated with serum bilirubin levels after adjustment for age, sex, body mass index (BMI), and smoking status (all P < 0.001). When stratified according to smoking status, these relationships were significant in never-smokers. Additionally, serum bilirubin level was negatively associated with the annual decline in FEV(1) and FVC, and positively associated with the annual decline in FEV(1)/FVC after adjustment for age, sex, BMI, baseline lung function, and smoking status (all P < 0.001). CONCLUSIONS: We found significant associations of serum bilirubin levels with FEV(1), FVC, and FEF(25–75%) in the general population, especially in never-smokers. Moreover, serum bilirubin levels were related with the annual decline in FEV(1), FVC, and FEV(1)/FVC ratio.