Garlic consumption has been associated inversely with esophageal cancer (EC); however, its interactions with tobacco smoking and alcohol consumption have never been evaluated in an epidemiological study. We evaluated the potential interactions between garlic intake and tobacco smoking as well as alcohol consumption in a population-based case-control study with 2969 incident EC cases and 8019 healthy controls. Epidemiologic data were collected by face-to-face interviews using a questionnaire. The adjusted odds ratio (OR) and 95% confidence interval (CI) were estimated and additive and multiplicative interactions were evaluated using unconditional logistic regression models, adjusting for potential confounding factors. Semi-Bayes (SB) adjustments were used to reduce potential false-positive findings. EC was associated inversely with raw garlic intake [SB-adjusted OR for more than once a week=0.68, 95% CI: 0.57-0.80], with a strong dose-response pattern in the overall analysis and in the stratified analyses by smoking and drinking. EC was associated positively with smoking and alcohol drinking, with SB-adjusted OR of 1.73 (95% CI: 1.62-1.85) and 1.37 (95% CI: 1.28-1.46) in dose-response effects of increased intensity and longer duration of smoking/drinking. Moreover, garlic intake interacts with smoking [synergy index (S)=0.83, 95% CI: 0.67-1.02; ratio of OR=0.88, 95% CI: 0.80-0.98] and alcohol drinking (S=0.73, 95% CI: 0.57-0.93; ratio of OR=0.86, 95% CI: 0.77-0.95) both multiplicatively and additively. Our findings suggested that high intake of raw garlic may reduce EC risk and may interact with tobacco smoking and alcohol consumption, which might shed a light on the development of EC as well as a potential dietary intervention among high-risk smokers and drinkers for EC prevention in the Chinese population.

Although the major risk factors for liver cancer have been established, preventive factors for liver cancer have not been fully explored. We evaluated the association between raw garlic consumption and liver cancer in a large population-based case-control study in Eastern China. The study was conducted in Jiangsu, China, from 2003 to 2010. A total of 2011 incident liver cancer cases and 7933 randomly selected population-controls were interviewed. Epidemiological data including raw garlic intake and other exposures were collected, and serum markers of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection were assayed. Overall, eating raw garlic twice or more per week was inversely associated with liver cancer, with an adjusted odds ratio (aOR) of 0.77 (95% confidence interval (CI): 0.62-0.96) compared to those ingesting no raw garlic or less than twice per week. In stratified analyses, high intake of raw garlic was inversely associated with liver cancer among Hepatitis B surface antigen (HBsAg) negative individuals, frequent alcohol drinkers, those having history of eating mold-contaminated food or drinking raw water, and those without family history of liver cancer. Marginal interactions on an additive scale were observed between low raw garlic intake and HBsAg positivity (attributable proportion due to interaction (AP) = 0.31, 95% CI: -0.01-0.62) and heavy alcohol drinking (AP = 0.28, 95% CI: 0.00-0.57). Raw garlic consumption is inversely associated with liver cancer. Such an association shed some light on the potential etiologic role of garlic intake on liver cancer, which in turn might provide a possible dietary intervention to reduce liver cancer in Chinese 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.

Background & aims

The potential interaction between family history of liver cancer and HBV infection on liver cancer has not been fully examined.

Methods

We conducted a population-based case-control study composed of 2011 liver cancer cases and 7933 controls in Jiangsu province, China from 2003 to 2010. Data on major risk or protective factors were collected and HBV/HCV sero-markers were assayed using blood samples. Semi-Bayes (SB) adjustments were applied to provide posterior estimates.

Results

Both family history of liver cancer (adjusted odds ratios [OR]: 4.32, 95% confidence intervals [CI]: 3.25-5.73) and hepatitis B surface antigen (HBsAg) positivity (adjusted OR: 9.94, 95% CI: 8.33-11.87) were strongly associated with liver cancer development. For individuals with different combinations of serological markers, the adjusted ORs were 8.45 (95% CI: 5.16-13.82) for HBsAg- and HBcAb-positive; 7.57 (95% CI: 4.87-11.77) for HBsAg-, HBeAg- and HBcAb-positive; and 3.62 (95% CI: 2.47-5.31) for HBsAg-, HBeAb- and HBcAb-positive, compared to all negatives in HBV serological markers. One log increase in HBV DNA level was associated with 17% increased risk (adjusted OR: 1.17, 95% CI: 1.03-1.32). The SB-adjusted OR of HBV-positive individuals with family history of liver cancer was 41.34 (95% posterior interval [PI]: 23.69-72.12) compared with those HBV-negative without family history. Relative excess risk due to additive interaction, the attributable proportion and synergy index were 73.13, 0.87 and 8.04 respectively. Adjusted ratio of OR for multiplicative interaction was 2.84 (95% CI: 1.41-5.75).

Conclusions

Super-additive and super-multiplicative interactions may exist between family history of liver cancer and HBV infection on the development of liver cancer.