Table 4.

Multivariate-adjusted RR of breast cancer in relation to updated smoking exposure variables stratified by vitamin A (retinol) and carotenoid tertiles (cumulative update of nutrients in 1991 and 1995)

Smoking variable	Vitamin A (retinol) tertiles (IU/day)					Total carotenoids tertiles (IU/day)
Smoking variable		1 (<1749)	2 (1749–3829)	3 (>3829)	1 (<6074)	2 (6068–10,167)	3 (>10,167)
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Years of smoking
<10	0.91	1.51	1.38	1.39	1.61	0.87
10–14	1.47	1.23	1.05	1.38	1.59	0.94
15–19	1.24	0.58	1.43	1.23	1.16	0.92
20+	1.29	1.28	1.01	1.68	1.30	0.78
P for trend	0.04	0.6	0.4	0.003	0.07	0.2
P for interaction			0.08			0.03
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
No. cigarettes for current smokers
1–4	0.39	1.17	0.89	1.61	1.35	0.62
5–14	1.43	1.47	1.06	2.02	0.55	1.08
15–24	1.68	0.77	0.98	1.62	1.33	0.61
25+	1.45	1.35	0.19	1.05	1.01	0.72
P for trend	0.02	0.7	0.2	0.2	0.8	0.2
P for interaction			0.4			0.08
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
No. cigarettes for past smokers
1–4	1.91	1.46	0.39	0.91	2.08	0.82
5–14	1.38	1.34	1.32	1.72	1.43	0.94
15–24	1.23	0.80	1.20	1.23	1.22	0.93
25+	1.29	0.83	1.47	1.46	1.59	1.03
P for trend	0.2	0.5	0.2	0.1	0.1	1.0
P for interaction			0.6			0.1
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Age at first smoking
<15	1.35	1.35	1.59	1.50	1.96	0.94
15–19	1.16	1.03	1.12	1.31	1.20	0.88
20+	1.41	1.17	0.96	1.56	1.32	0.86
P for interaction			0.7			0.05

	α-carotene tertiles (mg/day)					β-carotene tertiles (mg/day)
		1 (<432)	2 (432–819)	3 (>819)	1 (<2902)	2 (2902–4712)	3 (>4712)
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Years of smoking
<10	1.20	1.91	0.76	1.52	1.48	0.92
10–14	1.26	1.54	0.93	1.44	1.41	1.03
15–19	1.13	1.26	0.84	1.32	1.24	0.80
20+	1.50	1.27	0.81	1.77	1.10	0.87
P for trend	0.02	0.07	0.2	0.001	0.3	0.3
P for interaction			0.05			0.06
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
No. cigarettes for current smokers
1–4	0.64	1.10	0.49	0.77	0.67	0.69
5–14	1.56	1.60	0.74	2.13	0.77	1.23
15–24	1.74	1.01	0.70	1.90	1.20	0.58
25+	0.94	0.98	1.25	1.23	0.72	1.22
P for trend	0.2	1.0	0.9	0.07	0.8	0.9
P for interaction			0.3			0.1
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
No. cigarettes for past smokers
1–4	1.14	1.85	0.82	1.40	1.98	0.63
5–14	1.81	1.45	0.87	2.23	1.63	0.79
15–24	0.89	1.26	0.98	1.12	0.82	1.14
25+	1.43	1.44	1.83	1.19	1.25	1.14
P for trend	0.3	0.2	0.6	0.2	0.8	0.6
P for interaction			0.1			0.001
Never smokers (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Age at first smoking
<15	1.19	2.12	0.85	1.75	1.79	0.89
15–19	1.30	1.14	0.87	1.34	1.19
20+	1.41	1.35	0.83	1.84	0.97	0.86
P for interaction			0.02			0.03