Obesity ups risk of early-onset colorectal cancer

Obese people are more likely to develop early-onset colorectal cancer (CRC), suggests a study, noting that the increasing prevalence of obesity in younger generations may significantly contribute to the increase in this disease.

“The magnitude of the association of body mass index (BMI) with CRC risk for younger adults seems to be comparable with the association previously reported for all ages or specifically for older adults, suggesting that higher BMI might also be an important risk factor for early-onset CRC,” the researchers said.

The databases of PubMed, Embase, and Web of Science were systematically searched up to February 2021 for studies assessing the link between BMI (before diagnosis but not near diagnosis) and CRC risk and reporting specific results for early-onset CRC. The researchers then summarized results from studies with similar BMI groupings in meta-analyses using random-effects models.

Twelve studies met the eligibility criteria, of which six were pooled in meta-analyses. Results yielded a higher risk of early-onset CRC for overweight and obesity (BMI ≥25 kg/m²) compared with normal weight (odds ratio [OR], 1.42, 95 percent confidence interval [CI], 1.19–1.68). [Am J Clin Gastroenterol 2021;116:2173-2183]

Of note, such risk intensified with increasing BMI, with more robust risk for obesity (OR, 1.88, 95 percent CI, 1.40–2.54) than for overweight (OR, 1.32, 95 percent CI, 1.19–1.47).

These findings were similar to those from previous studies that assessed BMI and CRC risk at all ages, most of which occurs at older ages. [Cancer Epidemiol Biomarkers Prev 2007;16:2533-2547; Obes Rev 2010;11:19-30; World J Gastroenterol 2007;13:4199-4206]

No consistent pattern on the differences in the relationship of BMI with early-onset CRC was seen for sex-specific associations. In the older population, however, earlier studies reported a stronger association of BMI with CRC for men than for women. [Gut 2013;62:933-947; Lancet 2008;371:569-578; PLoS One 2013;8:e53916]

Some studies analysed the association of other indicators of obesity with early-onset CRC risk. For instance, Moore and colleagues found that a large waist circumference (≥99.1 and 101.6 cm for women and men, respectively) was independently associated with a twofold higher risk of colon cancer, with a robust association noted among sedentary individuals. [Int J Obes Relat Metab Disord 2004;28:559-567]

“Interventions aimed at preventing and enhancing the management of obesity in adolescents and younger adults, which are crucial for the prevention of many other adverse health outcomes, might also play a key role for reducing CRC incidence in younger and older adults, and should be a public health priority,” the researchers said.

The current study had certain limitations. Diverse timing of BMI assessment, different inclusion and exclusion criteria, and various covariate adjustment limited the comparability of the results from several studies. In addition, dose-response meta-analyses could not be performed due to the limited number of studies and information available for these studies.