Table 4.

Multivariable relative risk* of colorectal cancer in relation to frequency of bowel movement or laxative use according to years of onset in the Nurses’ Health Study

	Frequency of bowel movement				P for trend
	>1/day	daily	every 2 days	every 3 days or less
Colorectal cancer onset within10 years of assessment	42	301	66	30
	0.77 (0.55,1.07)	1.0 (Reference)	0.90 (0.69,1.18)	0.87 (0.59,1.27)	0.52
Colorectal cancer onset 11-18 years after assessment	55	380	103	46
	0.85 (0.64,1.13)	1.0 (Reference)	1.08 (0.86,1.34)	1.03 (0.85,1.26)	0.18
Colorectal cancer onset 19-28 years after assessment	72	474	125	43
	0.92 (0.71,1.18)	1.0 (Reference)	0.99 (0.81,1.21)	0.73 (0.54,1.01)	0.69
	Frequency of laxative				P for trend
	never	less than monthly	use monthly	weekly-daily
Colorectal cancer onset within 10 years of assessment	326	65	19	29
	1.0 (Reference)	0.79 (0.60,1.03)	0.92 (0.57,1.46)	0.93 (0.63,1.37)	0.82
Colorectal cancer onset 11-18 years after assessment	406	117	23	38
	1.0 (Reference)	1.15 (0.94,1.42)	0.93 (0.61,1.42)	1.03 (0.74,1.44)	0.91
Colorectal cancer onset 19-28 years after assessment	522	119	31	42
	1.0 (Reference)	0.95 (0.78,1.16)	0.98 (0.68,1.41)	0.98 (0.71,1.35)	0.93

Covariates are the same as those listed in Table 2.