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Lifestyle factors and colorectal cancer risk (1): systematic review and meta‐analysis of associations with body mass index
Author(s) -
Harriss D. J.,
Atkinson G.,
George K.,
Tim Cable N.,
Reilly T.,
Haboubi N.,
Zwahlen M.,
Egger M.,
Renehan A. G.
Publication year - 2009
Publication title -
colorectal disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.029
H-Index - 89
eISSN - 1463-1318
pISSN - 1462-8910
DOI - 10.1111/j.1463-1318.2009.01766.x
Subject(s) - medicine , colorectal cancer , body mass index , meta analysis , confidence interval , relative risk , observational study , obesity , oncology , demography , prospective cohort study , random effects model , cancer , sociology
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/m 2 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.