Smoking and obesity are associated with an increased risk of colorectal cancer

Gastroenterology and Hepatology

Colorectal cancer is one of the most common cancers in the world, ranking second in terms of incidence and third in terms of mortality in 2020. Despite the many treatments available, colorectal cancer is often diagnosed at an advanced stage, which complicates optimal therapeutic interventions. It is therefore essential to identify risk factors and implement primary prevention strategies.

In this study, the link between various factors (obesity, smoking, alcohol consumption, physical activity) and the risk of colorectal cancer was analysed. Data were obtained from several published genome-wide association studies (GWAS). Instrumental variables included nucleotide polymorphisms associated with obesity, smoking, alcohol consumption and physical activity. Data on colorectal cancer were collected from the FinnGen database, including 3022 people with colorectal cancer.

The results revealed that the obesity indicator WHR (waist-to-hip ratio) was associated with an increased risk of colorectal cancer when it was high. Obesity, and more precisely the distribution of body fat as measured by WHR, is confirmed as a risk factor for colorectal cancer.

The number of cigarettes per day and smoking initiation were also potentially associated with an increased risk of colorectal cancer. These results suggest a potential association between smoking and an increased risk of colorectal cancer, consistent with previous studies showing that smoking can increase the incidence of digestive cancers. Mechanisms such as smoking-induced dysbiosis of the intestinal microbiota and increased intestinal levels of taurodeoxycholic acid could explain this association.

However, no evidence was found to suggest that physical activity and alcohol consumption were associated with this type of cancer.

Regarding alcohol consumption, although some observational studies have found an association between moderate consumption and a reduced risk of colorectal cancer, this study did not. Similarly, despite evidence establishing the benefits of physical activity in cancer prevention, no causal association was found between physical activity and colorectal cancer in this study.

In conclusion, these results underline the importance of controlling smoking and maintaining a healthy weight for the prevention of colorectal cancer.

Source(s) :
Li X, Chang Z, Wang J, Ding K, Pan S, Hu H, Tang Q. Unhealthy lifestyle factors and the risk of colorectal cancer: a Mendelian randomization study. Sci Rep. 2024 Jun 15;14(1):13825. doi: 10.1038/s41598-024-64813-y. PMID: 38879601; PMCID: PMC11180165. ;

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