Case-control study of tobacco smoke exposure and breast cancer risk in Delaware

BMC Cancer

Table 2 Active smoking and breast cancer among cases and controls, Delaware, 2000–2002

	cases		controls		odds ratio^a	95% confidence interval^a
Active smoke exposure	n	%	n	%
Ever smoked 100 cigarettes
No	124	43.2	161	51.8	1.00	reference
Yes	163	56.8	150	48.2	1.43	1.03–1.99
Total years smoked cigarettes^b
<10	23	8.0	26	8.4	1.36	0.72–2.55
10–19	27	9.4	33	10.6	1.13	0.64–2.01
20–29	34	11.9	26	8.4	1.80	1.02–3.20
30–39	36	12.6	32	10.3	1.31	0.76–2.25
40–49	27	9.4	21	6.8	1.50	0.79–2.82
50–62	15	5.2	12	3.9	1.21	0.52–2.84
Average number of cigarettes/day^b
<10	58	20.5	49	15.9	1.60	1.01–2.53
10–19	67	23.7	58	18.8	1.53	0.99–2.35
20–29	25	8.8	29	9.4	1.12	0.61–2.04
30–68	9	3.2	12	3.9	0.84	0.34–2.08
Total pack-years^b
<5	37	13.1	36	11.7	1.45	0.85–2.45
5–9	19	6.7	18	5.8	1.65	0.81–3.35
10–19	37	13.1	26	8.4	1.83	1.04–3.23
20–29	28	9.9	29	9.4	1.24	0.69–2.24
30–39	10	3.5	12	3.9	1.06	0.44–2.56
40–49	16	5.7	9	2.9	1.92	0.81–4.55
50–102	12	4.2	18	5.8	0.75	0.34–1.65
Years smoked at or before age 18^c
<5	93	32.4	91	29.3	1.34	0.91–1.96
5–10	16	5.6	15	4.8	1.33	0.62–2.85
Years smoked, before first live birth^d
Never smokers	108	37.6	138	44.4	1.00	reference
<5	38	13.2	36	11.6	1.25	0.73–2.13
5–9	59	20.6	55	17.7	1.37	0.87–2.16
10–14	12	4.2	27	8.7	0.69	0.33–1.45
15–39	11	3.8	9	2.9	1.99	0.76–5.18

^a adjusted for age, education, and menopausal status
^b Numbers do not always total due to missing data
^c Excludes women who smoked only after age 18
^d Excludes nulliparous women and those who smoked only after the birth of their first child

ISSN: 1471-2407