Table 3.

Hazard Ratios for Incident Proximal and Distal Colon Cancer and Rectal Cancer (Competing-Risks Model) in Nurses’ Health Study, 1980–2010

Risk Factor	Proximal Colon (n = 821)			Distal Colon (n = 521)			Rectal (n = 376)			P Value
	HRa	95% CI	P Value	HRa	95% CI	P Value	HRa	95% CI	P Value	Proximal vs. Distal	Distal vs. Rectal	Proximal vs. Rectal
Age (years; 60 vs. 50)	2.01	1.83, 2.21	<0.0001	1.62	1.45, 1.81	<0.0001	1.71	1.50, 1.96	<0.0001	0.004	0.52	0.053
Family history of colon or rectal cancer (yes vs. no)b	1.55	1.31, 1.83	<0.0001	1.43	1.15, 1.79	0.002	1.26	0.96, 1.66	0.095	0.59	0.48	0.21
Red meat intake (servings/day per year; 1 vs. 0)	1.15	0.93, 1.42	0.19	0.82	0.61, 1.10	0.19	0.99	0.70, 1.40	0.96	0.068	0.089	0.47
Processed meat intake (servings/day per year; 1 vs. 0)	0.95	0.72, 1.26	0.72	1.45	1.06, 1.98	0.02	1.13	0.75, 1.71	0.57	0.050	0.35	0.50
Folate intake (µg/day per year; 600 vs. 200)	0.80	0.67, 0.96	0.016	0.92	0.74, 1.16	0.49	0.77	0.58, 1.02	0.071	0.35	0.095	0.79
Smoking history (total pack-years; 40 vs. 0)	1.31	1.16, 1.48	<0.0001	1.04	0.88, 1.23	0.66	1.27	1.05, 1.53	0.013	0.029	0.12	0.76
BMI (units per year; 30 vs. 20)c	1.35	1.10, 1.65	0.004	1.28	0.98, 1.67	0.067	1.50	1.10, 2.04	0.011	0.77	0.46	0.58
Physical activity level (MET-hours/week per year; 21 vs. 2)	0.64	0.47, 0.87	0.004	0.40	0.25, 0.64	0.0002	0.89	0.56, 1.41	0.63	0.11	0.017	0.23
Height (inches per year; 67 vs. 61)	1.24	1.04, 1.49	0.019	1.25	0.98, 1.60	0.070	1.24	0.93, 1.65	0.15	0.95	0.94	0.98
Alcohol intake (g/day per year; 30 vs. 0)	1.09	0.88, 1.36	0.43	1.05	0.77, 1.43	0.75	1.33	0.96, 1.85	0.088	0.84	0.30	0.33
Aspirin use (tablets per week per year; 7 vs. 0)	0.75	0.64, 0.87	0.0002	0.79	0.65, 0.97	0.023	0.80	0.63, 1.01	0.060	0.67	0.96	0.66
Endoscopic screening (yes vs. no; 20 years vs. 0)	0.96	0.84, 1.09	0.53	0.55	0.43, 0.69	<0.0001	0.48	0.36, 0.64	<0.0001	<0.0001	0.49	<0.0001
PMH use (vs. never users)
Current use	0.95	0.79, 1.14	0.59	0.79	0.63, 1.01	0.058	0.88	0.68, 1.15	0.35	0.24	0.56	0.65
Past use	0.98	0.83, 1.16	0.82	1.03	0.84, 1.28	0.75	0.79	0.61, 1.02	0.074	0.70	0.11	0.16
Calcium intake (mg/day per year; 1,000 vs. 500)	0.90	0.77, 1.04	0.14	0.65	0.53, 0.80	<0.0001	0.89	0.71, 1.13	0.36	0.15	0.049	0.99

Abbreviations: BMI, body mass index; CI, confidence interval; HR, hazard ratio; MET, metabolic equivalent; PMH, postmenopausal hormone.

^a For variables whose β coefficients were calculated per year, the relative risk accounts for 40 years (e.g., ages 30–70 years) and for the specified contrast. Relative risk = exp[β (40 years) (contrast)]. For dichotomous variables, the relative risk was calculated as exp(β).

^b Family history of colon or rectal cancer in a first-degree relative.

^c BMI was calculated as weight (kg)/height (m)².