Table 2.

Baseline characteristics of the study populations

Variable	Low-to-average risk of breast cancer (n = 119)		Unaffected BRCA1/2 carriers (n = 143)		P-value
	Mean (SD)	Range	Mean (SD)	Range
Age (years), mean (SD)	48.4 (9.3)	25–79	38.0 (8.6)	22–55	<.0001
Body mass index (BMI)a, mean (SD)	26.3 (5.8)	18.0–49.5	25.5 (5.4)	17.9–48.2	0.23
	n	%b	n	%
Race
Other	19	16.0	0	0.0	<.0001
White, non-Hispanic	100	84.0	143	100.0
Education level
High school	28	23.5	32	22.4	0.28
College degree	39	32.8	60	42.0
Graduate work	52	43.7	51	35.7
Cigarette smoking
Never	81	68.1	95	66.4	0.74
Former	31	26.1	36	25.2
Current	7	5.9	12	8.4
Age at menarche (years)
<12	18	15.3	19	13.4	0.91
12–13	73	61.9	90	63.4
≥14	27	22.9	33	23.2
Missing	1		1
Parous
No	31	26.1	66	46.2	0.001
Yes	88	73.9	77	53.8
Age at first birth (years)
<30	65	54.6	54	37.8	0.006
≥30 or nulliparous	54	45.4	89	62.2
Breastfed
Never	52	45.2	75	52.4	0.25
Ever	63	54.8	68	47.6
Missing	4		0
Oral contraceptives
Never	30	25.4	16	11.2	0.002
Former	78	66.1	99	69.2
Current	10	8.5	28	19.6
Missing	1		0
Menopausal status
Premenopausal	68	61.3	81	56.6	<.0001
Postmenopausal, natural	9	8.1	10	7.0
Postmenopausal, surgical	16	14.4	51	35.7
Postmenopausal, unknown	18	16.2	1	0.7
Missing	8		0
Hormone therapy
Never	81	68.6	101	70.6	0.93
Former	17	14.4	20	14.0
Current	20	16.9	22	15.4
Missing	1		0
SERMs
Never	115	97.5	133	93.0	0.24
Former	1	0.8	5	3.5
Current	2	1.7	5	3.5
Missing	1		0
Prior breast biopsy
0	83	69.7	108	75.5	0.57
1	25	21.0	25	17.5
2+	11	9.2	10	7.0

SERM selective estrogen receptor modulator

P-values < 0.05 are in bold type

^aBMI = Weight (kg)/height² (m²)

^bMissing values were excluded from percentage calculations