C-CLEAR: Colorectal Cancer, Lifestyle, Exercise and Research
Lifestyle factors and colorectal cancer risk (1): systematic review and meta-analysis of associations with body mass index
Article first published online: 17 JAN 2009
© 2009 The Authors. Journal Compilation © 2009 The Association of Coloproctology of Great Britain and Ireland
Volume 11, Issue 6, pages 547–563, July 2009
How to Cite
Harriss, D. J., Atkinson, G. , George, K., Tim Cable, N., Reilly, T., Haboubi, N., Zwahlen, M., Egger, M., Renehan, A. G. and the C-CLEAR group (2009), Lifestyle factors and colorectal cancer risk (1): systematic review and meta-analysis of associations with body mass index. Colorectal Disease, 11: 547–563. doi: 10.1111/j.1463-1318.2009.01766.x
- Issue published online: 10 JUN 2009
- Article first published online: 17 JAN 2009
- Received 7 August 2008; accepted 26 August 2008
- Body mass index;
- colorectal cancer risk;
- systematic review
Objective Excess body weight, defined by body mass index (BMI), may increase the risk of colorectal cancer. As a prerequisite to the determination of lifestyle attributable risks, we undertook a systematic review and meta-analysis of prospective observational studies to quantify colorectal cancer risk associated with increased BMI and explore for differences by gender, sub-site and study characteristics.
Method We searched MEDLINE and EMBASE (to December 2007), and other sources, selecting reports based on strict inclusion criteria. Random-effects meta-analyses and meta-regressions of study-specific incremental estimates were performed to determine the risk ratio (RR) and 95% confidence intervals (CIs) associated with a 5 kg/m2 increase in BMI.
Results We analysed 29 datasets from 28 articles, including 67 361 incident cases. Higher BMI was associated with colon (RR 1.24, 95% CIs: 1.20–1.28) and rectal (1.09, 1.05–1.14) cancers in men, and with colon cancer (1.09, 1.04–1.12) in women. Associations were stronger in men than in women for colon (P < 0.001) and rectal (P = 0.005) cancers. Associations were generally consistent across geographic populations. Study characteristics and adjustments accounted for only moderate variations of associations.
Conclusion Increasing BMI is associated with a modest increased risk of developing colon and rectal cancers, but this modest risk may translate to large attributable proportions in high-prevalence obese populations. Inter-gender differences point to potentially important mechanistic differences, which merit further research.