Interaction between tobacco smoking and hepatitis B virus infection on the risk of liver cancer in a <scp>C</scp>hinese population

Although tobacco smoking has been reported as a risk factor for liver cancer, few studies have specifically explored the association among Chinese females and the potential interaction between smoking and other risk factors. A population-based case-control study was conducted and 2,011 liver cancer cases and 7,933 healthy controls were enrolled in Jiangsu, China from 2003 to 2010. Epidemiological data were collected, and serum hepatitis B surface antigen (HBsAg) and anti-HCV antibody were measured. Unconditional logistic regression was used to examine association and potential interaction, while semi-Bayes (SB) method was employed to make estimates more conservative. The prevalence of serum HBsAg positivity was 43.2% among cases and 6.5% among controls. The adjusted odds ratios (OR) for ever smoking were 1.62 (95% confidence interval [CI]: 1.33-1.96) among male and 0.82 (95% CI: 0.53-1.26) among female. Age at first cigarette, duration of smoking and pack-years of smoking were all significantly associated with liver cancer among men. Compared to HBsAg-negative never smokers, the adjusted ORs were 1.25 (95% CI: 1.03-1.52) for HBsAg-negative ever smokers, 7.66 (95% CI: 6.05-9.71) for HBsAg-positive never smokers, and 15.68 (95% CI: 12.06-20.39) for HBsAg-positive ever smokers. These different odds ratios indicated super-additive (RERI: 7.77, 95% CI: 3.81-11.73) and super-multiplicative interactions (ROR: 1.64, 95% CI: 1.17-2.30) between hepatitis B virus (HBV) infection and tobacco smoking. Most associations and interactions detected remained statistically significant after SB adjustments. Tobacco smoking and HBV infection positively interact in the development of liver cancer.