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

Table 3 Results of univariate analysis for rectal cancer (cases n = 112, controls n = 560)

factors	OR	95%CI	χ2	P
drining mixed water source (y = 1, n = 0)	2.021		1.170	3.491	6.363	0.011
mucious blood history (y = 1, n = 0)	2.138	1.122	4.072	5.335	0.021
defaecation drug using (y = 1, n = 0)	2.280	0.711	7.312	1.923	0.166
cholecyst excision history (y = 1, n = 0)	2.294	0.715	7.352	1.195	0.163

In Table 2, it was showed that four variables, well water drinking, mixed water source drinking, chronic diarrhea history and intestinal polyp history, were significantly associated with colon cancer (P < 0.05). The factor of appendicitis history showed an OR value close to significant level (P = 0.066). For rectal cancer in Table 3, there were two variables reached the significant level of P = 0.05, which were mixed water source drinking (OR = 2.02) and mucous blood stool history (OR = 2.14).