Table 1.

Distribution of selected characteristics among controls and cases, ER+, ER-/PR-/HER2- breast cancer.

Characteristic	Control		Cases
			Total		Subtypes a				p-value *
	(n = 938)		(n = 960)		ER+ b (n = 778)		ER-/PR-/HER2-(n = 182)
	n	%	n	%	n	%	n	%
Age (years)
20-29	25	2.7%	22	2.3%	15	1.9%	7	3.8%
30-34	86	9.2%	77	8.0%	55	7.1%	22	12.1%
35-39	267	28.5%	257	26.8%	199	25.6%	58	31.9%
40-44	560	59.7%	604	62.9%	509	65.4%	95	52.2%	0.05
Reference (years)
2004-2005	306	32.6%	273	28.4%	212	27.2%	61	33.5%
2006-2007	360	38.4%	330	34.4%	273	35.1%	57	31.3%
2008-2010	272	29.0%	357	37.2%	293	37.7%	64	35.2%	0.002
Race/ethinicity
Non-Hispanic white	767	81.9%	749	78.4%	607	78.5%	142	78.0%
African American	34	3.6%	49	5.1%	32	4.1%	17	9.3%
Asian/Pacific Islannder	82	8.8%	113	11.8%	99	12.8%	14	7.7%
Native American	19	2.0%	26	2.7%	19	2.5%	7	3.8%
Hispanic White	35	3.7%	18	1.9%	16	2.1%	2	1.1%	< 0.001
Missing	1		5		5		0
Education
High school or less	98	10.4%	113	11.8%	89	11.4%	24	13.2%
Post high-school/some college	305	32.5%	318	33.1%	253	32.5%	65	35.7%
College graduate	354	37.7%	352	36.7%	283	36.4%	69	37.9%
Graduate/Professional school	181	19.3%	177	18.4%	153	19.7%	24	13.2%	0.5
First-degree family history of breast cancer
No	814	89.9%	742	80.0%	602	80.3%	140	78.7%
Yes	91	10.1%	186	20.0%	148	19.7%	38	21.3%	< 0.001
Missing	33		32		28		4
BMI (kg/m2)
<25.0	532	57.0%	571	59.7%	473	61.0%	98	54.1%
25.0-29.9	232	24.8%	226	23.6%	182	23.5%	44	24.3%
≥30.0	170	18.2%	159	16.6%	120	15.5%	39	21.5%	0.2
Missing	4		4		3		1
Duration of oral contraceptives use (years)
Never	103	11.0%	107	11.2%	92	11.9%	15	8.4%
<5.0	338	36.1%	340	35.7%	281	36.3%	59	33.0%
5.0-9.9	218	23.3%	194	20.4%	155	20.0%	39	21.8%
≥10	276	29.5%	312	32.7%	246	31.8%	66	36.9%	0.3
Missing	3		7		4		3
Parity number
Nulliparous	191	20.4%	259	27.0%	209	26.9%	50	27.5%
1	193	20.6%	192	20.0%	158	20.3%	34	18.7%
2	365	38.9%	351	36.6%	283	36.4%	68	37.4%
≥3	189	20.1%	157	16.4%	127	16.3%	30	16.5%	0.05
Missing	0		1		1		0
Age at first livebirth among parous women (years)
<25	218	29.2%	225	32.2%	168	29.6%	57	43.2%
25-29	225	30.1%	222	31.8%	187	33.0%	35	26.5%
30-34	204	27.3%	173	24.7%	143	25.2%	30	22.7%
≥35	100	13.4%	79	11.3%	69	12.2%	10	7.6%	0.04
Missing	0		2		2		0
Age at menarche (years)
<12	190	20.3%	214	22.3%	170	21.9%	44	24.2%
12-13	519	55.4%	538	56.1%	438	56.4%	100	54.9%
≥14	227	24.3%	207	21.6%	169	21.8%	38	20.9%	0.6
Missing	2		1		1		0
Alcohol consumption (average number of alcohol drinks / week)
Never	227	24.3%	220	23.1%	175	22.7%	45	24.9%
0-1.4	234	25.1%	223	23.4%	189	24.5%	34	18.8%
1.4-3.7	235	25.2%	245	25.7%	196	25.4%	49	27.1%
≥3.7	237	25.4%	265	27.8%	212	27.5%	53	29.3%	0.6
Missing	5		7		6		1
Ever had a screening mammogram
Never	478	51.0%	399	41.6%	315	40.5%	84	46.2%
Ever	460	49.0%	561	58.4%	463	59.5%	98	53.8%	<0.001

Abbreviations: BMI, body mass index. ER, estrogen receptor. PR, progesterone receptor. HER2, human epidermal growth factor receptor 2.

^*Chi-squared.

^aER-/HER2+ were excluded because of limited number (60 cases).

^bRegardless of PR/HER2 status.