Abstract
OBJECTIVES: Smoking is a risk factor for gastric cancer. Studies have shown that the risk of gastric cancer can vary by smoking status and smoking amount at a single point in time. However, few data have been reported about the effect of changes in smoking status over time on the risk of gastric cancer. METHODS: This study collected data from the National Health Insurance Corporation in Korea on 97,700 Korean men without gastric cancer who underwent health check-ups from 2002 to 2013. The smoking status (never smoked, quit smoking, and currently smoking) of study participants was assessed in 2003-2004 and 2009, and the results were categorized into 7 groups: never-never, never-quit, never-current, quit-quit, quit-current, current-quit, and current-current. Participants were followed until 2013 to identify incident gastric cancer. A multivariate Cox proportional hazard model was used to calculate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident gastric cancer according to changes in smoking status and smoking amount (pack-years). RESULTS: Compared with group 1 (never-never), participants currently smoking in 2009 (never-current, quit-current, and current-current) had higher HRs for gastric cancer (never-quit: 1.077; 95% CI, 0.887 to 1.306, never-current: 1.347; 95% CI, 0.983 to1.846, quit-quit: 1.086; 95% CI, 0.863 to 1.366, quit-current: 1.538; 95% CI, 1.042 to 2.269, current-quit: 1.339; 95% CI, 1.077 to 1.666, and current-current: 1.589; 95% CI, 1.355 to 1.864, respectively). The risk for gastric cancer was highest in heavy smokers, followed by moderate smokers. CONCLUSIONS: In all categories of smoking status, current smoking was associated with the highest risk of gastric cancer. Heavy smoking was associated with an increased risk of gastric cancer, even in former smokers.