Table 5. Relative risks for colorectal cancer according to tobacco smoking.

	Men, smoking status
	Never smoked	Smokers ⩽20 pack-years	Smokers >20 pack-years	P for trend
Colon cancer
Person-years	16 702	42 141	37 361
Cases, n	16	41	47
Age-adjusted RRs (CI)	1.00	1.33 (0.78–2.28)	1.43 (0.85–2.41)	0.09
Multivariate RRs (CI)	1.00	1.36 (0.79–2.33)	1.37 (0.81–2.32)	0.19
Rectal cancer
Person-years	16 653	42 009	37 327
Cases, n	7	16	34
Age-adjusted RRs (CI)	1.00	1.22 (0.54–2.78)	2.36 (1.13–4.92)	0.03
Multivariate RRs (CI)	1.00	1.33 (0.57–3.12)	2.44 (1.12–5.30)	0.04
	Women, smoking status
	Never smoked	Smokers ⩽10 pack-years	Smokers >10 pack-years	P for trend
Colon cancer
Person-years	82 430	8944	7273
Cases, n	68	4	5
Age-adjusted RRs (CI)	1.00	0.65 (0.24–1.76)	0.97 (0.39–2.40)	0.91
Multivariate RRs (CI)	1.00	0.59 (0.21–1.62)	0.77 (0.30–1.96)	0.54
Rectal cancer
Person-years	82 266	8944	7264
Cases, n	32	4	2
Age-adjusted RRs (CI)	1.00	1.69 (0.59–4.86)	1.06 (0.25–4.47)	0.47
Multivariate RRs (CI)	1.00	1.76 (0.60–5.14)	0.94 (0.21–4.16)	0.63
Multivariate=adjusted for age, height, BMI, alcohol intake, and years of education.