Exercise can reduce the risk of colorectal cancer

        Evidence from observational epidemiological studies shows that an increase in physical activity (PA) corresponds to a decrease in the risk of colorectal cancer. And there is ample evidence that there is a protective association between recreational PA and colorectal cancer. The meta-analysis showed that occupational activities, recreational activities, transportation-related PA, and occupational sedentary behaviors were all associated with a lower risk of colorectal cancer.
        Although there is currently strong evidence about the impact of PA on the risk of colorectal cancer, related observational studies cannot be attributed to this due to the influence of confounding factors or residual confounding. In addition, in observational studies, PA is usually measured as a form of self-reported activity.
        In this study, researchers used a Mendelian randomized (MR) study to investigate whether PA reduces the risk of colorectal cancer and explore the contribution of changes in body fat.
        Self-reported moderate to severe PA (MVPA), acceleration vector amplitude PA (AMPA), and common genetic variants associated with sedentary time were used as instrumental variables in this study. In order to control the confounding effects of obesity, the researchers included relevant instrumental variables for body mass index (BMI), body fat percentage, waist circumference and fat ratio of arms, trunk, and legs. Through the MR study design, the role of these instrumental variables in the genome-wide association study of colorectal cancer was analyzed. The study included 31,197 cases and 61,770 controls.

Forest plot reveals factors related to the risk of colorectal cancer

        The results showed that MVPA and AMPA reduced the risk of colorectal cancer as measured by genetic methods, which was mediated by genetic measurement of obesity. The odds ratio and 95% confidence interval (CI) for each standard deviation increase of MVPA and AMPA were 0.56 (0.31, 1.01) and 0.60 (0.41, 0.88), respectively.
        Further research has shown that there is no correlation between sedentary time and the risk of colorectal cancer. For MVPA and AMPA, the proportions of BMI-mediated effects were 2% (95% CI: 0, 14) and 32% (95% CI: 12, 46), respectively.
        All in all, the results of the study provide strong evidence for strengthening public health measures to prevent colorectal cancer. The researchers suggest that regardless of body fat status, promoting the development of PA in the population may be beneficial to reducing the risk of colorectal cancer.


Original source:

Zhang， X.， Theodoratou， E.， Li， X. et al. Genetically predicted physical activity levels are associated with lower colorectal cancer risk： a Mendelian randomisation study. Br J Cancer (29 January 2021).