Table 3.

Associations^a Between Breast Cancer Risk Factors and Breast Cancer Diagnosis, According to Method of Detection, Collaborative Breast Cancer Study, 1992–2007

Characteristic	No. of Controlsb (n = 17,602)	Mammography-Detected Breast Cancer			Woman/Clinician-Detected Breast Cancer			P Valuec
		No. of Casesb (n = 8,372)	OR	95% CI	No. of Casesb (n = 7,276)	OR	95% CI
First-degree family history of breast cancer
No	15,130	6,474	1	Referent	5,769	1	Referent
Yes	2,472	1,898	1.57	1.47, 1.69	1,507	1.67	1.55, 1.80	0.16
Age at menarche, years
<12	3,384	1,844	1	Referent	1,435	1	Referent
12	4,330	2,168	0.93	0.86, 1.01	1,856	0.97	0.89, 1.06	0.38
13	4,815	2,277	0.88	0.81, 0.95	1,982	0.92	0.84, 1.00	0.38
≥14	5,074	2,082	0.79	0.73, 0.86	2,003	0.85	0.78, 0.93	0.12
Age at first birthd, years
<20	3,082	1,118	1	Referent	1,100	1	Referent
20–24	7,698	3,483	1.18	1.09, 1.29	2,866	1.03	0.95, 1.12	0.01
25–29	3,504	1,849	1.39	1.26, 1.53	1,544	1.13	1.02, 1.25	0.001
≥30	1,378	833	1.62	1.43, 1.84	779	1.32	1.16, 1.49	0.01
Parity
0	1,941	1,088	1	Referent	987	1	Referent
1	1,670	862	0.69	0.60, 0.79	845	0.88	0.76, 1.01	0.01
2	4,852	2,452	0.68	0.60, 0.76	2,199	0.82	0.73, 0.93	0.01
≥3	9,139	3,970	0.59	0.53, 0.66	3,244	0.70	0.63, 0.78	0.01
Age at menopausee, years
<45	3,576	1,412	1	Referent	1,109	1	Referent
45–49	3,283	1,643	1.23	1.10, 1.37	1,255	1.22	1.10, 1.35	0.92
50–54	4,536	2,521	1.31	1.19, 1.43	1,934	1.39	1.26, 1.53	0.30
≥55	1,686	997	1.32	1.18, 1.48	676	1.31	1.16, 1.49	0.94
Postmenopausal hormone usef
Never use	3,063	1,154	1	Referent	1,176	1	Referent
Estrogen only	1,293	521	0.89	0.78, 1.01	506	1.23	1.08, 1.40	<0.0001
Estrogen plus progestin only	845	497	1.14	0.99, 1.31	422	1.49	1.29, 1.72	0.002
Other	360	186	1.02	0.84, 1.25	154	1.23	1.00, 1.52	0.13
Alcohol consumption, drinks/ week
0	3,685	1,600	1	Referent	1,482	1	Referent
0.1–6.9	11,620	5,530	1.06	0.99, 1.14	4,727	0.99	0.92, 1.07	0.12
≥7	2,296	1,242	1.24	1.13, 1.37	1,067	1.14	1.03, 1.25	0.14
Postmenopausal BMIg,h
<18.5	151	30	0.61	0.40, 0.92	68	1.05	0.77, 1.44	0.02
18.5–24.9	3,063	1,154	1	Referent	1,176	1	Referent
25.0–29.9	2,637	1,278	1.31	1.18, 1.45	914	0.91	0.82, 1.01	<0.0001
≥30.0	1,736	1,058	1.72	1.54, 1.92	732	1.13	1.01, 1.27	<0.0001
Premenopausal BMIi
<18.5	62	6	0.29	0.12, 0.67	42	1.08	0.72, 1.63	0.003
18.5–24.9	2,197	811	1	Referent	1,283	1	Referent
25.0–29.9	1,280	558	1.19	1.04, 1.37	621	0.82	0.72, 0.92	<0.0001
≥30.0	983	424	1.21	1.04, 1.40	356	0.61	0.52, 0.71	<0.0001

Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio.

^a ORs were mutually adjusted for all other risk factors in the table, in addition to age, state of residence, year of diagnosis, menopausal status, educational level, history of mammography utilization, and interaction terms for interactions between BMI, postmenopausal hormone use, and menopausal status.

^b Average value from 5 imputed data sets.

^c Test for difference in the risk factor association by method of detection.

^d Among parous women only.

^e Among postmenopausal women only.

^f Among normal-weight postmenopausal women.

^g Weight (kg)/height (m)².

^h Among postmenopausal women who had never used postmenopausal hormones.

ⁱ Among premenopausal women only.