Shaw, EileenFarris, Megan SStone, Chelsea RDerksen, Jeroen W GJohnson, RhysHilsden, Robert JFriedenreich, Christine MBrenner, Darren R2018-09-262018-09-262018-01-11BMC Cancer. 2018 Jan 11;18(1):71http://hdl.handle.net/1880/107879https://doi.org/10.11575/PRISM/45862Abstract Background Physical activity is consistently associated with a reduced risk of colorectal cancer in epidemiologic studies. This association among higher risk subgroups, such as those with a first-degree family history of colorectal cancer or high body mass index remains unclear. Methods We searched MEDLINE for studies examining physical activity and colorectal cancer risk among higher risk subgroups through July 11, 2017. Fifteen and three studies were eligible for inclusion for body mass index and first-degree family history of colorectal cancer subgroups, respectively. Estimates of the highest to lowest comparison of physical activity for each subgroup of risk were pooled using random-effects models. Results The pooled associations of physical activity and colorectal cancer risk for those without and with a first-degree family history of colorectal cancer were 0.56 (95% confidence interval (CI) = 0.39–0.80) and 0.72 (95% CI = 0.39–1.32), respectively (pheterogeneity = 0.586). The pooled associations of physical activity and colorectal cancer risk for the low and high body mass index groups were 0.74 (95% CI = 0.66–0.83) and 0.65 (95% CI = 0.53–0.79), respectively (pheterogeneity = 0.389). Conclusions Overall, a stronger relative risk of physical activity on colorectal cancer risk was observed in the higher body mass index group, although the difference was not statistically significant, suggesting an added benefit of physical activity as a cancer prevention strategy in population groups with strong risk factors for colorectal cancer. Additional research among these subgroups is warranted.Journal Article2018-09-26enThe Author(s).https://doi.org/10.1186/s12885-017-3970-5