The joint effects of major lifestyle factors on colorectal cancer risk among Chinese men: A prospective cohort study

Previous studies have suggested individual healthy lifestyle factors are related to lower risk of colorectal cancer. Their joint effects, however, have rarely been investigated. We aimed to assess the combined lifestyle impact on colorectal cancer risk and to estimate the population attributable risks of these lifestyle factors. Using data from the Shanghai Men's Health Study (2002-2013), we constructed healthy lifestyle index composing the following lifestyle factors: smoking, alcohol consumption, diet, waist-hip ratio and exercise participation. Cox proportional hazards models were used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs). Over a median of 9.28 years' follow-up, 671 colorectal cancer cases occurred (400 colon cancer and 274 rectal cancer) among 59,503 men. Each increment of healthy lifestyle index was associated with a 17% lower risk of colorectal cancer (HR=0.83, 95% CI: 0.78, 0.89), 10% of colon cancer (HR=0.90, 95% CI: 0.83, 0.99) and 27% of rectal cancer (HR=0.73, 95% CI: 0.66, 0.82). If all men in the cohort followed a lifestyle as defined by these five factors, 21% colorectal cancer cases would have been prevented (PAR=21%, 95% CI: 4%, 36%). In conclusion, combined lifestyle factors are significantly related to lower risk of colorectal cancer and the effects are more pronounced on rectal cancer than on colon cancer.