Risk factors for sporadic colorectal cancer in southern Chinese

Table 1 Distributions of selected variables in colorectal cancer patients and cancer-free controls n (%)

Variables	Test group		Validation group		Merged group		P1
	Case	Control	Case	Control	Case	Control
Age (yr)							0.992
≤ 49	120 (23.4)	122 (23.3)	36 (18.7)	36 (18.0)	156 (22.1)	158 (21.9)
50-60	146 (28.5)	149 (28.5)	39 (20.2)	42 (21.0)	185 (26.2)	191 (26.4)
> 60	247 (48.2)	252 (48.2)	118 (61.1)	122 (61.0)	365 (51.7)	374 (51.7)
Sex							0.937
Male	300 (58.5)	300 (57.4)	137 (71.0)	149 (74.5)	437 (61.9)	449 (62.1)
Female	213 (41.5)	223 (42.6)	56 (29.0)	51 (25.5)	269 (38.1)	274 (37.9)
Smoking status							< 0.0001
Current	228 (44.4)	142 (27.2)	88 (45.6)	77 (38.5)	316 (44.8)	219 (30.3)
Former	59 (11.5)	79 (15.1)	20 (10.4)	24 (12.0)	79 (11.2)	103 (14.3)
Non	226 (44.1)	302 (57.7)	85 (44.0)	99 (49.5)	311 (44.1)	401 (55.5)
Drinking status							< 0.0001
Current	275 (53.6)	83 (15.9)	98 (50. 8)	57 (28.5)	373 (52.8)	140 (19.4)
Former	14 (2.7)	25 (4.8)	12 (6.2)	10 (5.0)	26 (3.7)	35 (4.8)
Non	224 (43.7)	415 (79.4)	83 (43.0)	133 (66.5)	307 (43.5)	548 (75.8)
Family history of cancer							0.018
Yes	71 (13.8)	57 (10.9)	20 (10.4)	8 (4.0)	91 (12.9)	65 (9.0)
No	442 (86.2)	466 (89.1)	173 (89.6)	192 (96.0)	615 (87.1)	658 (91.0)
BMI (kg/m2)							0.002
≤ 23.9	297 (57.9)	346 (66.2)	92 (47. 7)	118 (59.0)	389 (55.1)	464 (64.2)
24.0-27.9	169 (32.9)	139 (26.6)	77 (39.9)	66 (33.0)	246 (34.8)	205 (28.4)
≥ 28.0	47 (9.2)	38 (7.3)	24 (12.4)	16 (8.0)	71 (10.1)	54 (7.5)
Menstrual history							0.881
Premenopause	43 (20.2)	41 (18.4)	10 (17.9)	11 (21.6)	53 (19.7)	52 (19.0)
Menopause	170 (79.8)	182 (81.6)	46 (82.1)	40 (78.4)	216 (80.3)	222 (81.0)

¹P value for two-sided χ² test.

Table 2 Comparison of epidemiological factors for colorectal cancer

Variables	Adjusted OR (95% CI)1
	Test group	Validation group	Merged group
Smoking status
Non	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Former	0.97 (0.52-1.80)	0.66 (0.30-1.46)	0.78 (0.49-1.23)
Current	1.41 (0.82-2.43)	0.79 (0.45-1.38)	1.01 (0.69-1.48)
Trend test P value	< 0.00001	0.187	< 0.00001
Drinking status
Non	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Former	2.02 (0.93-4.41)	2.84 (1.03-7.81)	2.30 (1.27-4.17)
Current	14.69 (9.41-22.94)	3.82 (2.23-6.56)	8.61 (6.15-12.05)
Trend test P value	< 0.00001	0.023	< 0.00001
Family history of cancer
Negative	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Positive	1.43 (0.94-2.18)	3.21 (1.31-7.84)	1.62 (1.12-3.34)
BMI (kg/m2)
≤ 23.9	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
≥ 24.0	1.34 (1.00-1.78)	1.60 (1.05-2.44)	1.39 (1.10-1.75)

¹Adjusted for age, sex, smoking status, alcohol drinking, family history of cancer, BMI.

Table 3 Stratification analysis of colon and rectal cancer

Variables	Adjusted OR (95% CI)1
	Test group		Validation group		Merged group
	Colon cancer (n = 253)	Rectal cancer (n = 260)	Colon cancer (n = 95)	Rectal cancer (n = 98)	Colon cancer (n = 348)	Rectal cancer (n = 358)
Smoking status
Non	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Former	0.71 (0.34-1.49)	1.26 (0.59-2.69)	1.09 (0.44-2.72)	0.41 (0.14-1.18)	0.83 (0.48-1.43)	0.79 (0.45-1.38)
Current	1.34 (0.72-2.51)	1.87 (0.96-3.65)	1.03 (0.53-2.03)	0.78 (0.40-1.51)	1.22 (0.78-1.91)	1.17 (0.75-1.83)
Drinking status
Non	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Former	2.28 (0.90-5.76)	1.32 (0.48-3.64)	2.51 (0.78-8.06)	3.10 (0.88-10.92)	2.51 (1.24-5.07)	1.71 (0.80-3.65)
Current	13.24 (7.78-22.51)	11.91 (7.14-19.87)	3.46 (1.83-6.53)	3.61 (1.94-6.74)	7.60 (5.13-11.25)	7.52 (5.13-11.01)
Family history of cancer
Negative	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
Positive	1.67 (1.01-2.75)	1.26 (0.76-2.09)	3.26 (1.12-9.45)	3.52 (1.26-9.85)	1.82 (1.17-2.82)	1.51 (0.97-2.35)
BMI (kg/m2)
≤ 23.9	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)	1.00 (ref.)
≥ 24.0	1.48 (1.05-2.09)	1.22 (0.86-1.73)	1.18 (0.70-1.99)	2.00 (1.18-3.36)	1.38 (1.04-1.83)	1.35 (1.02-1.79)

¹Adjusted for age, sex, smoking status, alcohol drinking, family history of cancer, BMI.