Table 6.

The effects of various covariates on age of diagnosis

Current smoking status	n	Crude average age	Crude differencea	Adjusted differenceb
Current smoking status, period #1 only (1957–1965)
Never smoker	(384)	66.0	Reference	Reference
Former smoker(quit >5 years prior to diagnosis)	(31)	64.7	−1.3	−1.9
Former smoker(quit 5 years or less prior to diagnosis)	(39)	63.1	−2.9*	−3.0*
Current smoker	(195)	58.4	−7.6*	−7.6*
		P for trend	<0.01	<0.01

Current smoking status	n	Crude average age	Crude differencea	Adjusted differencec
Current smoking status, Period #3 only (1982–1997)
Never smoker	(546)	64.1	Reference	Reference
Former smoker(quit >5 years prior to diagnosis)	(499)	64.3	0.2	−0.2
Former smoker(quit 5 years or less prior to diagnosis)	(158)	61.0	−3.1*	−2.8*
Current smoker	(192)	60.0	−4.1*	−4.0*
		P for trend	<0.01	<0.01

* P < 0.05

^aRestricted to those not missing any of the covariates used for the adjusted difference

^bAdjusted for body mass index, weekly vegetable intake and weekly meat intake

^cAdjusted for family history of colorectal cancer, body mass index, weekly vegetable intake and weekly meat intake