Metabolic risk factors of colorectal cancer: Umbrella review

The association between metabolic factors and colorectal cancer (CRC) risk is inconclusive. This umbrella review aimed to summarise and describe the association using existing systematic reviews and/or meta-analyses.

Four databases (Medline, Scopus, Web of Science, and Cochrane Library) were searched for systematic reviews and/or meta-analyses of observational studies. Two independent authors extracted data on the summary estimated effect and heterogeneity of studies using I² from the individual reviews. The Assessing the Methodological Quality of Systematic Reviews (AMSTAR 2) tool was used to evaluate the methodological quality.

49 articles were included in this review. Although most included studies were graded with critically low methodological quality (81.6 %), we found a significant positive association between obesity (summary relative risk (SRR) range 1.19-1.49), diabetes mellitus (SRR range 1.20-1.37), hypertension (SRR range 1.07-1.62), metabolic syndrome (SRR range 1.25-1.36), non-alcoholic fatty liver disease (pooled odds ratio (POR) range 1.13-1.56), and risk of CRC. Higher serum high-density lipoprotein cholesterol levels were associated with a lower risk of CRC in 3/6 reviews, while others did not find any association. There was no clear association between high triglyceride levels, total cholesterol levels, low-density lipoprotein cholesterol levels, and risk of CRC.

This umbrella review identified that most metabolic factors are significantly associated with increased risk of CRC. Thus, people affected by metabolic factors may be benefited from CRC screening and surveillance.