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Meta-Analysis
. 2013;8(1):e53916.
doi: 10.1371/journal.pone.0053916. Epub 2013 Jan 17.

Obesity and risk of colorectal cancer: a systematic review of prospective studies

Yanlei Ma  1 , Yongzhi Yang, Feng Wang, Peng Zhang, Chenzhang Shi, Yang Zou, Huanlong Qin
Affiliations
Meta-Analysis

Obesity and risk of colorectal cancer: a systematic review of prospective studies

Yanlei Ma et al. PLoS One. 2013.

Abstract

Background: Mounting evidence indicates that obesity may be associated with the risk of colorectal cancer (CRC). To conduct a systematic review of prospective studies assessing the association of obesity with the risk of CRC using meta-analysis.

Methodology/principal findings: Relevant studies were identified by a search of MEDLINE and EMBASE databases before January 2012, with no restrictions. We also reviewed reference lists from retrieved articles. We included prospective studies that reported relative risk (RR) estimates with 95% confidence intervals (CIs) for the association between general obesity [measured using body mass index (BMI)] or central obesity [measured using waist circumference (WC)] and the risk of colorectal, colon, or rectal cancer. Approximately 9, 000, 000 participants from several countries were included in this analysis. 41 studies on general obesity and 13 studies on central obesity were included in the meta-analysis. The pooled RRs of CRC for the obese vs. normal category of BMI were 1.334 (95% CI, 1.253-1.420), and the highest vs. lowest category of WC were 1.455 (95% CI, 1.327-1.596). There was heterogeneity among studies of BMI (P<0.001) but not among studies of WC (P=0.323).

Conclusions: Both of general and central obesity were positively associated with the risk of CRC in this meta-analysis.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Flow diagram of the literature search process.
CRC, colorectal cancer; BMI, body mass index; WC, waist circumference.
Figure 2
Figure 2. Adjusted relative risks of colorectal cancer for the obese vs. normal category of BMI.
The size of each square is proportional to the weight of the study (inverse of variance). CI, confidence interval; BMI, body mass index; C, colon cancer; R, rectal cancer; F, female; M, male.
Figure 3
Figure 3. Adjusted relative risks of colorectal cancer for the highest vs. lowest categories of WC.
The size of each square is proportional to the weight of the study (inverse of variance). CI: confidence interval; WC, waist circumference; C, colon cancer; R, rectal cancer; F, female; M, male.
Figure 4
Figure 4. Begg’s funnel plot for Identification of publication bias in all studies for the obese vs. normal category of BMI and risk of colorectal cancer.
Figure 5
Figure 5. Begg’s funnel plot for Identification of publication bias in all studies for the highest vs. lowest categories of WC and risk of colorectal cancer.
See this image and copyright information in PMC

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