[Nested case-control study on the risk factors of colorectal cancer].

OBJECTIVE

To investigate the risk factors of colorectal cancer.

METHODS

A nested case-control study was conducted based on a cohort of 64,693 subjects in Jiashan county, Zhejiang, China. One hundred and ninety-six cases of colorectal cancer were detected during a follow-up program for 10 years. Nine hundred and eighty non-colorectal cancer subjects were randomly selected from the cohort as controls. Univariate analysis and mutivariate non-conditional logistic regression were used to analyse associations between the exposure factors and colorectal cancer.

RESULTS

The age of case group was significantly older than that of the control group. Moreover, the age at diagnose of colon cancer was significantly older than that of the rectal cancer. Other than age, the final regression model showed that mucous blood stool history and colon polyp history were significantly associated with colon cancer (OR = 2.961, 95% CI:1.202-7.298 and 8.941, 95% CI:1.820-43.926, respectively) while mixed sources of drinking water was found to be associated with rectal cancer with a OR value of 1.823 (95% CI:1.024-3.247).

CONCLUSION

The risk factors of colon cancer were different from that of the rectal cancer. Age was an important factor influencing the incidence of both colon cancer and rectal cancer. Mucous blood stool history and colon polyp history were associated with colon cancer, while drinking mixed water was closely associated with rectal cancer.