Abstract
PURPOSE: The purpose of this study was to investigate the effect of smoking habit change on the risk of cancer. MATERIALS AND METHODS: From the Korean National Health Insurance Service database, we determined the change in smoking habit between the first (2002 and 2003) and second (2004 and 2005) health examination periods. A total of 143,071 men were categorized into baseline heavy (≥ 20 cigarettes per day), moderate (10-19 cigarettes per day), light (< 10 cigarettes per day) smokers, quitters, and never smokers, after which the change in smoking status was determined during the second health examination. The participants were then followed up from 2006 to 2013 for all cancer, smoking related cancer, and lung cancer. RESULTS: Compared to heavy continual smokers, heavy smokers who quit had reduced risk of smoking related cancer (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.56 to 0.97) and tended to have reduced risk of all cancer (HR, 0.87; 95% CI, 0.75 to 1.00). Moderate smokers who reduced the amount of smoking to light levels had decreased risk of all cancer (HR, 0.82; 95% CI, 0.72 to 0.94), smoking related cancer (HR, 0.74; 95% CI, 0.59 to 0.93), and lung cancer (HR, 0.55; 95% CI, 0.38 to 0.79) compared to heavy continual smokers. CONCLUSION: Smoking reduction decreases the risk of all cancer, smoking related cancer, and lung cancer. While smoking cessation should be the treatment of choice for smokers, smoking reduction may serve as an alternative strategy for those who cannot quit.