Physical activity, polygenic risk score, and colorectal cancer risk

Whether and to what extent the relationship between physical activity (PA) and colorectal cancer (CRC) differs according to CRC-related genetic risk remains to be determined, and no studies to date have quantified how much genetically determined risk could be compensated for with active exercise.

Genetic risk was quantified by a polygenic risk score (PRS) summarizing the estimated effect of 140 CRC-associated genetic variants. Associations of PA with CRC risk were estimated by multivariable logistic regression across PRS levels. We also compared the impact of PA and specific PA types to the PRS using "genetic risk equivalent (GRE)", a novel approach to enhance effective risk communication.

Among 5058 CRC patients and 4134 controls, we observed no significant association between overall PA level in quartiles and CRC risk. However, the highest versus lowest lifetime leisure time physical activity (LTPA) was associated with a 13% lower CRC risk [odds ratio 0.87, 95% confidence interval (CI) 0.77-1.00] independent of PRS levels (adjusted p value for interaction = 0.18). This effect was equivalent to the effect of having 11 percentiles lower PRS (GRE -10.6, 95% CI -20.7 to -0.6). The GRE (95% CI) for the highest lifetime sports tertile was -23.0 (-33.9 to -12.0).

LTPA was inversely associated with CRC risk irrespective of polygenic risk for CRC, which reinforces the importance of LTPA in CRC prevention among the general population. Adequate sports activity can compensate for a large share of polygenic risk for CRC.