Moderate alcohol consumption protects against colorectal adenomas in smokers

Background: Although some studies have shown an association between alcohol consumption and colorectal adenomas, the effect of moderate alcohol consumption is not well defined, nor is the interaction between alcohol and smoking. Aim: To investigate the relationship between different levels of alcohol consumption and colorectal adenomas and to determine whether smoking modifies this relationship. Methods: Eligible patients who underwent a complete colonoscopy were included (179 cases and 466 controls). Alcohol consumption was obtained from a lifestyle questionnaire. Patients were divided into three groups: (1) Abstainers: 0 drinks/week; (2) Moderate drinkers: > 0 to <7 drinks/week; (3) Heavy drinkers: > 7 drinks/week. Odds ratios (OR) were calculated using logistic regression, controlling for gender, age, body mass index, use of non-steroidal anti-inflammatory medications. Results were stratified by the number of years smoked. Results: The proportion of patients with adenomas was 29.6% in abstainers, 22.1% in moderate drinkers, and 36.7% in heavy drinkers. The relationship between alcohol consumption and colorectal adenomas varied significantly by smoking history. For individuals who had never smoked, heavy drinkers were at significantly increased odds of having an adenoma compared to moderate drinkers (OR 3.08; 95% CI: 1.50-6.32), while no difference was seen for abstainers (OR 0.99; 95% CI: 0.52-1.89). Similarly, among individuals who had smoked 1-14 years, heavy drinkers were at increased odds of having an adenoma compared to moderate drinkers (OR 2.61; 95% CI: 1.04-6.51), and no difference was seen for abstainers (OR 1.02; 95% CI: 0.33-3.10). Somewhat unexpectedly, among individuals who had smoked for 15 or more years, abstainers were at increased odds of having an adenoma compared to moderate drinkers (OR 2.04; 95% CI: 0.91-4.59), while heavy drinkers were not at increased odds of having an adenoma (OR 0.73; 95% CI: 0.27-1.97). Conclusions: Consumption of less than seven alcohol drinks per week does not increase the risk of having a colorectal adenoma. We found evidence in this study that moderate alcohol consumption among long-term smokers may potentially decrease the risk of an adenoma compared to abstainers.