Effects of physical activity on colorectal cancer risk among family history and body mass index subgroups: a systematic review and meta-analysis

Abstract

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 (p_{heterogeneity} = 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 (p_{heterogeneity} = 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.

Keywords: Body mass index; Colorectal neoplasms; Exercise; Family history; Risk.

Fig. 1

Flow diagram of systematic review and meta-analysis of physical activity and risk of colorectal cancer with higher risk subgroups

Fig. 2

Adjusted relative risk estimates of physical activity and colorectal cancer risk stratified by family history, listed in chronological order (p-value across subgroups = 0.586). All estimates are for both sexes. * Family history subgroup-specific case numbers were not described for Slattery (1997) [37], thus total cases were used for case numbers from this study

Fig. 3

Adjusted relative risk estimates of physical activity and colorectal cancer risk stratified by BMI subgroups, listed in chronological order

Fig. 4

Funnel plot of study estimates of colorectal cancer risk with physical activity by high and low BMI subgroups