N Cases	Null Model	Model 1	Model 2	Model 3
RR (95% confidence interval)
Proximal	4319
Black/White			1.32 (1.24,1.41)	1.23 (1.14,1.33)	1.24(1.15,1.34)
Male/Female			1.16(1.09,1.23)	1.16(1.09,1.23)	1.16(1.09,1.23)
45–54/35–44 y			3.17 (2.59,3.87)	3.16 (2.59,3.87)	3.16 (2.59,3.87)
55–64/35–44 y			7.85 (6.49,9.49)	7.82 (6.47,9.46)	7.83 (6.48,9.47)
65+/35–44 y			23.71 (19.76,28.45)	23.57 (19.64,28.28)	23.59 (19.66,28.30)
CDI				1.07 (1.03,1.12)
White					1.10(1.04,1.17)
Black					1.04 (0.99,1.10)
σv		0.060	0.021	0.018	0.011
X2/df		1.42	1.17	1.16	1.14
Distal	2642
Black/White			1.34 (1.23,1.45)	1.20(1.09,1.32)	1.22 (1.11,1.34)
Male/Female			1.49(1.38,1.61)	1.50(1.39,1.62)	1.50(1.39,1.62)
45–54/35–44 y			3.36 (2.74,4.13)	3.35 (2.73,4.12)	3.36 (2.73,4.12)
55–64/35–44 y			6.50 (5.33,7.92)	6.47 (5.31,7.88)	6.48 (5.32,7.90)
65+/35–44 y			12.38 (10.22,14.99)	12.27 (10.13,14.85)	12.28 (10.14,14.88)
CDI				1.11 (1.06,1.17)
White					1.19(1.11,1.28)
Black					1.04(0.97,1.11)
σv		0.038	0.015	0.008	0.006
X2/df		1.18	1.02	1.01	0.97
Rectal	2970
Black/White			1.16(1.07,1.26)	1.04 (0.95,1.15)	1.05 (0.96,1.16)
Male/Female			1.72 (1.60,1.85)	1.72 (1.60,1.85)	1.72 (1.60,1.85)
45–54/35–44 y			3.41 (2.86,4.06)	3.40 (2.85,4.05)	3.40 (2.85,4.05)
55–64/35–44 y			5.64 (4.75,6.69)	5.61 (4.73,6.66)	5.62 (4.74,6.67)
65+/35–44 y			8.84 (7.49,10.44)	8.77 (7.42,10.35)	8.77 (7.43,10.36)
CDI				1.12 (1.07,1.18)
White					1.16(1.08,1.24)
Black					1.08 (1.01,1.16)
Tract Variance		0.072	0.061	0.053	0.017
X2/df		1.14	0.98	0.98	0.96