Cigarette smoking, alcohol consumption, and risk of colorectal cancer in South Korea: A case-control study

The current case-control study comprehensively evaluated the status, quantity, and duration of smoking and alcohol drinking for both men and women, considering the subsites of colorectal cancer. A total of 925 colorectal cancer cases and 2775 controls were included in the analysis. Odds ratios (OR) and 95% confidence intervals (CI) were computed by logistic regression models adjusting for potential confounders. In men, the risk of colorectal cancer significantly increased for heavy smokers who smoked ≥40 pack-years (OR 1.74, 95% CI 1.22–2.50), ≥40 years (OR 1.50, 95% CI 1.05–2.16), or ≥40 cigarettes/day (OR 1.92, 95% CI 1.04–3.54). Men showed a significant increase in risk, especially for rectal cancer with an increasing amount or duration of smoking. In women, distal colon cancer risk increased in smokers who smoked ≥20 years (OR 3.21, 95% CI 1.27–8.14) or ≥20 cigarettes/day (OR 4.75, 95% CI 1.09–20.57). Additionally, female smokers who smoked ≥20 cigarettes/day had an increased risk of rectal cancer (OR 6.46, 95% CI 1.64–25.46). Regarding the association of cigarettes smoked per day and the risk of rectal cancer, there was no significant difference between men and women (gender interaction p value = 0.14). Compared with never-drinkers, those who consumed alcohol at ≥40 g/day in men and ≥20 g/day in women had an OR of 2.39 (95% CI 1.68–3.41) and 3.52 (95% CI 1.56–7.96), respectively. The effect of daily alcohol consumption (g of ethanol/day) on cancer risk was not significantly different among subsites. Association of alcohol consumption quantity (g of ethanol/day) and the risk of proximal and distal colon cancer were stronger in women than in men (gender interaction p value < 0.01). There was no significant interaction in the multiplicative level when alcohol consumption and cigarette smoking were combined. The duration and amount of smoking as well as the amount of alcohol consumption were associated with an elevated risk of colorectal cancer in both men and women.