Table 1. The characteristics of the study population.

Variables	Case (N = 641) No. (%)	Control (N = 1037) No. (%)	P
Sex			0.748b
Male	384 (59.9)	613 (59.1)
Female	257 (40.1)	424 (40.9)
Age	56.31±12.59a	57.24±10.86a	0.119c
Tumor site
Colon	250 (39.0)
Rectum	391 (61.0)
Tumor differentiation
Poorly	80 (12.5)
Moderately	445 (69.4)
Well	116 (18.1)

^aAge was represented as mean±standard deviation.

^b P value was calculated by the x ² test.

^c P value was calculated by the t test.