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Table 4
Case-only odds ratios and 95% confidence intervals from logistic regression models^aof associations between breast cancer tumor subtypes and demographic, reproductive, and lifestyle risk factors, combined LACE and Pathways Studies (n = 2544)
	Luminal A (comparison)	Triple negative^a			HER2-overexpressing^a

	n	n	OR	95% CI	n	OR	95% CI

Age at diagnosis (years)
≥ 65 (Ref)	637	68	Ref	---	23	Ref	---
50 to 64	871	115	1.99	0.85, 1.62	45	1.39	0.83, 2.32
< 50	355	105	2.78	1.99, 3.90	25	1.75	0.97, 3.15
Test for trend				P ≤ 0.0001			P = 0.03
Race/ethnicity
White (Ref)	1464	204	Ref	---	60	Ref	---
African American	92	44	3.14	2.12, 4.66	5	1.25	0.49, 3.21
Hispanic	135	21	0.93	0.57, 1.53	13	2.19	1.16, 4.13
Asian	135	12	0.53	0.28, 0.97	12	2.02	1.05, 3.88
Other	37	7	1.28	0.56, 2.94	3	1.95	0.58, 6.52
Menopausal status
Postmenopausal (Ref)	1283	163	Ref	---	57	Ref	---
Premenopausal	406	91	0.84	0.55, 1.27	21	0.65	0.31, 1.33
Family history
No (Ref)	1453	229	Ref	---	80	Ref	---
Yes	410	59	0.95	0.69, 1.29	13	0.62	0.34, 1.13
Age at first full-term pregnancy (years)
Nulliparous (Ref)	335	52	Ref	---	13	Ref	---
< 26	959	163	1.28	0.90, 1.82	61	2.02	1.07, 3.80
≥ 26	567	72	0.93	0.63, 1.38	18	0.86	0.42, 1.79
Parity
Nulliparous (Ref)	335	52	Ref	---	13	Ref	---
1 to 2 children	837	137	1.11	0.78, 1.58	40	1.30	0.68, 2.47
≥ 3 children	691	99	1.18	0.81, 1.72	40	1.82	0.94, 3.53
Lifetime duration of breastfeeding
Never (Ref)	871	148	Ref	---	43	Ref	---
0 to 3 months	255	41	1.04	0.71, 1.52	16	1.29	0.71, 2.35
≥ 4 months	711	97	0.78	0.59, 1.03	32	0.86	0.54, 1.38
Parity among never breastfed^b
Nulliparous (Ref)	321	50	Ref	---	12	Ref	---
1 to 2 children	326	59	1.34	(0.87, 2.08)	15	1.52	(0.68, 3.41)
≥ 3 children	²²⁴	39	1.68	(1.00, 2.81)	16	3.03	(1.27, 7.23)
Parity among 0 to 3 months breastfed^b
1 to 2 children (Ref)	144	25	Ref	---	9	Ref	---
≥ 3 children	108	16	1.16	(0.53, 2.56)	7	1.82	(0.57, 5.80)
Parity among ≥ 4 months breastfed^b
1 to 2 children (Ref)	358	52	Ref	---	14	Ref	---
≥ 3 children	352	44	0.99	(0.63, 1.55)	17	1.23	(0.57, 2.66)
Alcohol use
Never (Ref)	709	110	Ref	---	39	Ref	---
Ever	880	129	0.98	0.73, 1.30	40	0.94	0.59, 1.50
Smoking history
Never (Ref)	921	146	Ref	---	51	Ref	---
≤ 10	251	41	0.95	0.65, 1.40	7	0.51	0.23, 1.14
11 to 19	147	21	0.89	0.54, 1.47	8	1.17	0.54, 2.56
≥ 20	531	78	0.98	0.72, 1.34	26	1.05	0.63, 1.73
Hormone replacement therapy (postmenopausal only)
Never (Ref)	314	50	Ref	---	24	Ref	---
Ever	943	112	0.83	0.57, 1.20	33	0.45	0.26, 0.79
Oral contraceptive use
Never (Ref)	647	80	Ref	---	29	Ref	---
Ever	1160	202	0.97	0.72, 1.31	63	1.12	0.69, 1.83
BMI (kg/m²)^c
< 25 (Ref)	785	110	Ref	---	39	Ref	---
25 to 29	563	99	1.33	0.98, 1.81	31	1.21	0.74, 1.99
≥ 30	500	77	1.04	0.75, 1.45	23	1.03	0.59, 1.78
BMI (kg/m²) among premenopausal^b
< 25 (Ref)	223	39	Ref	---	7	Ref	---
25 to 29	99	28	1.82	1.03, 3.24	7	2.15	0.70, 6.58
≥ 30	81	23	1.97	1.03, 3.77	7	2.51	0.74, 8.51
BMI (kg/m²) among postmenopausal^b
< 25 (Ref)	480	59	Ref	---	25	Ref	---
25 to 29	422	60	1.08	0.73, 1.59	18	0.86	0.46, 1.61
≥ 30	372	43	0.76	0.49, 1.17	14	0.76	0.38, 1.51

^aAdjusted for age at diagnosis, race/ethnicity, and Pathways/LACE study origin except in models with age at diagnosis or race/ethnicity as main predictors. ^bP for interaction not statistically significant (P > 0.05) in any tumor subtype model. ^cBMI, body mass index one year pre-diagnosis (LACE) and around diagnosis (Pathways). CI = confidence interval; HER2 = human epidermal growth receptor 2; OR = odds ratio.
Kwan et al. Breast Cancer Research 2009 11:R31 doi:10.1186/bcr2261

Table 4