Cigarette Smoking and Adenomatous Polyps: A Meta-analysis

Background & Aims: Through the past 2 decades, a consistent association between cigarette smoking and colorectal adenomatous polyps, recognized precursor lesions of colorectal cancer, has been shown. We performed a meta-analysis to provide a quantitative pooled risk estimate of the association, focusing on the different characteristics of the study populations, study designs, and clinical feature of the polyps. Methods: We performed a comprehensive literature search of studies linking cigarette smoking and adenomas. We used random effects models to evaluate pooled relative risks and performed dose-response, heterogeneity, publication bias, and sensitivity analyses. Results: Forty-two independent observational studies were included in the analysis. The pooled risk estimates for current, former, and ever smokers in comparison with never smokers were 2.14 (95% confidence interval [CI], 1.86–2.46), 1.47 (95% CI, 1.29–1.67), and 1.82 (95% CI, 1.65–2.00), respectively. The association was stronger for high-risk adenomas than for low-risk adenomas. Studies in which all controls underwent full colonoscopy showed a higher risk compared with studies in which some or all controls underwent partial colon examination. Conclusions: This meta-analysis provides strong evidence of the detrimental effect of cigarette smoking on the development of adenomatous polyps. Smoking is important for both formation and aggressiveness of adenomas.

Abbreviations used in this paper: CI, confidence interval, CRC, colorectal cancer, RR, relative risk