Alcohol and smoking linked to higher risk of early-onset colorectal cancer, large review finds

03.06.2025 - A systematic review and meta-analysis published in Clinical Colorectal Cancer has found that both alcohol consumption and smoking are significant risk factors for developing colorectal cancer at an earlier age. The research comes amid rising incidence rates of early-onset colorectal cancer (EOCRC), defined as cases diagnosed at 55 years old or younger.

Clear Associations Across Multiple Studies

Researchers led by Janine Wieser and colleagues at the German Cancer Research Center analyzed data from eleven studies on alcohol and twelve on smoking, aiming to clarify the links between these modifiable lifestyle factors and EOCRC. Their comprehensive review included studies from North America, Europe, Asia, and Australia, focusing on adjusted estimates to ensure reliable results.

The meta-analysis found that alcohol use was associated with a 39% higher risk of EOCRC (pooled odds ratio [OR] 1.39; 95% confidence interval [CI] 1.14–1.69) compared to non-use. Notably, a dose-response relationship was identified: for every 10 grams of ethanol consumed daily, the risk of EOCRC increased by approximately 2.35% (OR per 10g/d ethanol 1.02, 95% CI 1.01–1.08).

Smoking was also found to be a significant risk factor. Ever-smokers (including current and former smokers) had a 39% higher risk of EOCRC compared to never-smokers (OR 1.39, 95% CI 1.20–1.59). The effect was strongest for ever-smoking (OR 1.59, 95% CI 1.36–1.85), while former smoking alone was not associated with an increased risk.

Implications for Public Health and Prevention

The study’s authors highlight the growing trend of colorectal cancer diagnoses among younger adults, despite overall declines in older populations due to screening programs. Their findings reinforce the role of alcohol and tobacco as modifiable risk factors that should be addressed in prevention strategies targeting younger age groups.

“In conclusion, our data indicate that alcohol consumption and smoking is associated with an increased risk of EOCRC. Public health interventions aimed at reducing smoking and alcohol consumption among young adults could also prevent EOCRC,” the researchers write.

Study Strengths and Limitations

The review is notable for its robust methodology, including pre-registration, independent screening by multiple reviewers, and detailed subgroup analyses. However, the authors note limitations such as reliance on self-reported data and the relatively small number of high-quality studies specifically on EOCRC. Potential publication bias was also identified, and the evidence regarding smoking was rated as lower in certainty compared to alcohol.

Growing Evidence for Lifestyle-Related Cancer Risk

These results add to the body of evidence linking lifestyle choices to cancer risk at increasingly younger ages. While previous studies had been inconsistent regarding smoking and EOCRC, this analysis provides stronger support for its role, along with a clear dose-response effect for alcohol.

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The full study, titled Associations of alcohol use and smoking with early-onset colorectal cancer - A systematic review and meta-analysis, is available open access in Clinical Colorectal Cancer. https://doi.org/10.1016/j.clcc.2025.05.002