Table 1.

Selected Characteristics of Premenopausal Breast Cancer Cases and Controls: Collaborative Breast Cancer Study (1996–2001)

		Cases (n = 1,706)*		Controls (n = 1,756)*		P†
		No.	%	No.	%
Education
	Less than high school	33	2.0	53	3.0
	High school graduate	570	33.7	539	30.7
	Some college	475	28.1	512	29.2
	College graduate	614	36.3	650	37.1	0.08
Parity
	Nulliparous	274	16.1	255	14.5
	1–2	996	58.4	943	53.7
	3–4	400	23.5	513	29.2
	≥5	36	2.1	45	2.6	0.001
Age at first birth‡
	<20 yrs	190	13.3	246	16.4
	20 – <25 yrs	462	32.3	557	37.1
	25 – <30 yrs	497	34.7	442	29.5
	≥30 yrs	283	19.8	256	17.1	0.0003
Family history of breast cancer
	No	1371	81.6	1555	89.8
	Yes	310	18.4	176	10.2	<.0001
Body mass index (kg/m2)
	<25	971	58.5	930	54.6
	25 – <30	430	25.9	474	27.8
	≥30	259	15.6	300	17.6	0.07
Mammogram in the last 5 years
	No	477	28.2	427	24.4
	Yes	1213	71.8	1326	75.6	0.01
Benign breast disease
	No	1174	69.8	1355	78.0
	Yes	508	30.2	383	22.0	<.0001

^*Unequal column totals reflect missing data.

^†χ²-test for differences between cases and controls.

^‡Only includes parous women.