Table 2.

Age- and BMI-adjusted linear regression results for the association between participant characteristics and volume and area mammographic density measures^a, The BREAST Stamp Project, 2007–2010 (n = 413)

		Percent mammographic density measures						Absolute mammographic density measures
		% FGV			PD			FGV (cm³)			DA (cm²)
Characteristic	N	β	SE	P	β	SE	P	β	SE	P	β	SE	P
Age at mammogram (years)
39–44	81	Ref.			Ref.			Ref.			Ref.
45–49	109	−0.04	0.19	0.84	0.03	0.25	0.90	0.21	0.50	0.68	0.14	0.31	0.64
50–54	102	−0.36	0.19	0.06	−0.14	0.25	0.59	−0.24	0.51	0.63	0.14	0.31	0.65
55–59	68	−1.14	0.21	<0.0001	−0.86	0.28	0.002	−1.55	0.56	0.006	−0.64	0.34	0.07
60–65	53	−0.91	0.23	<0.0001	−1.06	0.30	0.0005	−0.66	0.61	0.28	−0.76	0.37	0.04
P value for trend		<0.0001			<0.0001			*0.01*			*0.0065*
Race
White, non-Hispanic	383	Ref.			Ref.			Ref.			Ref.
Other	30	0.50	0.25	0.04	0.80	0.32	0.01	−0.05	0.65	0.94	0.56	0.40	0.16
Education level
<High school or high school grad	63	Ref.			Ref.			Ref.			Ref.
College/graduate school degree	347	0.19	0.18	0.28	0.44	0.23	0.06	0.56	0.47	0.23	0.56	0.28	0.048
Height (inches)^b
51–62	113	Ref.			Ref.			Ref.			Ref.
63–65	168	0.04	0.20	0.85	0.20	0.25	0.41	−0.87	0.43	0.04	−0.04	0.26	0.88
66–72.5	132	0.11	0.22	0.62	0.43	0.26	0.10	−0.79	0.45	0.08	0.09	0.27	0.74
P value for trend		0.62			0.09			0.09			0.72
Weight (pounds)^b
90–136	134	Ref.			Ref.			Ref.			Ref.
137–166	141	−1.10	0.16	<0.0001	−1.07	0.21	<0.0001	1.25	0.42	0.003	−0.17	0.25	0.50
167–338.5	138	−2.61	0.16	<0.0001	−2.62	0.21	<0.0001	1.62	0.42	0.0001	−1.02	0.25	<0.0001
P value for trend		<0.0001			<0.0001			*0.0001*			<0.0001
BMI, kg/m²
<25	196	Ref.			Ref.			Ref.			Ref.
25–<30	105	−1.40	0.16	<0.0001	−1.31	0.21	<0.0001	1.32	0.42	0.002	−0.21	0.25	0.41
30+	112	−2.52	0.15	<0.0001	−2.67	0.20	<0.0001	1.79	0.41	<0.0001	−1.07	0.25	<0.0001
P value for trend		<0.0001			<0.0001			<0.0001			<0.0001
Age at menarche (years)
≤12	153	Ref.			Ref.			Ref.			Ref.
13	150	0.28	0.15	0.06	0.47	0.19	0.02	0.28	0.39	0.47	0.43	0.24	0.08
≥14	104	0.21	0.16	0.19	0.24	0.21	0.25	0.01	0.44	0.97	0.08	0.27	0.75
P value for trend		0.15			0.17			0.95			0.65
Parity
Nulliparous	98	Ref.			Ref.			Ref.			Ref.
1	58	0.10	0.22	0.66	0.20	0.28	0.48	0.54	0.57	0.35	0.55	0.35	0.11
2	164	0.11	0.17	0.52	−0.17	0.22	0.43	0.04	0.43	0.93	−0.03	0.27	0.92
3+	92	0.08	0.19	0.66	−0.13	0.25	0.60	−0.62	0.50	0.21	−0.16	0.30	0.61
P value for trend		0.59			0.37			0.23			0.39
Age at first birth (years)
<30	217	Ref.			Ref.			Ref.			Ref.
Nulliparous or 30+	195	0.14	0.13	0.30	0.20	0.17	0.24	0.41	0.34	0.23	0.13	0.21	0.53
P value for trend		0.13			0.87			0.44			0.54
Oral contraceptives
Never	58	Ref.			Ref.			Ref.			Ref.
Former	335	−0.11	0.18	0.55	−0.02	0.23	0.92	−0.32	0.47	0.49	−0.17	0.29	0.55
Current	14	0.28	0.39	0.46	0.36	0.50	0.48	0.79	1.02	0.44	0.39	0.62	0.53
Menopausal status
Premenopausal	250	Ref.			Ref.			Ref.			Ref.
Postmenopausal	163	−0.84	0.20	<0.0001	−0.79	0.27	0.004	−1.47	0.55	0.007	−0.80	0.33	0.02
Age at menopause (years)
Premenopausal	250	0.89	0.32	0.006	0.35	0.42	0.40	1.71	0.85	0.04	0.32	0.52	0.53
≤45	32	0.23	0.35	0.51	−0.15	0.46	0.74	0.37	0.93	0.69	−0.28	0.57	0.62
46–49	34	0.11	0.34	0.75	−0.62	0.45	0.17	0.12	0.92	0.89	−0.86	0.56	0.13
50–52	23	Ref.			Ref.			Ref.			Ref.
53+	21	0.11	0.39	0.77	−0.46	0.51	0.37	0.53	1.04	0.61	−0.49	0.63	0.44
Postmenopausal, age unknown	53	−0.08	0.32	0.81	−0.61	0.42	0.15	0.34	0.85	0.69	−0.51	0.52	0.32
Menopausal hormone therapy
Never	303	Ref.			Ref.			Ref.			Ref.
Former	77	0.05	0.18	0.79	−0.05	0.23	0.83	−0.78	0.46	0.10	−0.27	0.28	0.34
Current	20	0.38	0.31	0.23	0.004	0.41	0.99	−0.56	0.82	0.49	−0.43	0.50	0.39
Missing/unknown	13	0.39	0.37	0.29	0.67	0.48	0.16	1.16	0.97	0.23	0.85	0.59	0.15
Cigarette smoking, 100+ cigarettes/lifetime
Never	203	Ref.			Ref.			Ref.			Ref.
Ever	201	−0.30	0.13	0.02	−0.45	0.17	0.008	0.22	0.34	0.52	−0.21	0.21	0.31
Breast biopsy before enrollment
Never	269	Ref.			Ref.			Ref.			Ref.
Ever	140	0.32	0.14	0.02	0.62	0.18	0.0004	0.55	0.36	0.12	0.71	0.22	0.001
Family history of breast cancer in a first-degree female relative
0	305	Ref.			Ref.			Ref.			Ref.
1+	103	0.18	0.15	0.23	0.08	0.19	0.69	0.56	0.39	0.15	0.11	0.24	0.65
Lump at the time of mammography
No	357	Ref.			Ref.			Ref.			Ref.
Yes	52	0.23	0.19	0.24	0.64	0.25	0.01	−0.76	0.51	0.14	0.49	0.31	0.12
Reason for mammography
Screening	326	Ref.			Ref.			Ref.			Ref.
Short-interval follow-up	21	−0.05	0.29	0.87	0.61	0.38	0.11	−0.42	0.77	0.58	0.61	0.47	0.20
Evaluation of breast problem	61	0.13	0.18	0.46	0.51	0.24	0.03	−0.61	0.48	0.20	0.45	0.29	0.12
BI-RADS breast density
I (entirely fat)	56	Ref.			Ref.			Ref.			Ref.
II (scattered densities)	183	0.51	0.17	0.002	1.60	0.18	<0.0001	0.64	0.51	0.21	2.15	0.26	<0.0001
III (heterogeneously dense)	131	1.47	0.18	<0.0001	3.35	0.20	<0.0001	1.56	0.56	0.01	3.72	0.29	<0.0001
IV (extremely dense)	33	2.81	0.25	<0.0001	4.79	0.27	<0.0001	2.85	0.78	0.0003	4.67	0.39	<0.0001
P value for trend		<0.0001			<0.0001			<0.0001			<0.0001
Final BI-RADS mammography assessment
3 (probably benign finding)	26	Ref.			Ref.			Ref.			Ref.
4 (suspicious abnormality)	363	0.29	0.26	0.27	0.23	0.34	0.51	0.73	0.68	0.29	0.35	0.42	0.40
5 (highly suggestive of malignancy)	23	−0.03	0.37	0.93	0.27	0.48	0.58	0.26	0.98	0.79	0.33	0.60	0.58
P value for trend		0.96			0.53			0.68			0.50
Biopsy type
Ultrasound-guided	195	Ref.			Ref.			Ref.			Ref.
Stereotactic-guided	208	0.16	0.13	0.23	0.13	0.17	0.46	0.36	0.34	0.29	0.15	0.21	0.49
Both	7	0.41	0.50	0.41	0.20	0.66	0.76	2.63	1.32	0.047	0.88	0.81	0.28
Biopsy laterality
Left	203	Ref.			Ref.			Ref.			Ref.
Right	210	−0.25	0.13	0.05	0.21	0.17	0.20	−1.42	0.33	<0.0001	0.12	0.21	0.55
Pathologic diagnosis
Benign	141	Ref.			Ref.			Ref.			Ref.
Proliferative	171	0.10	0.15	0.51	−0.06	0.19	0.75	0.28	0.39	0.47	−0.01	0.24	0.96
Proliferative with atypia	32	0.55	0.26	0.03	0.81	0.33	0.02	0.81	0.68	0.24	0.71	0.41	0.09
In-situ	34	−0.09	0.25	0.73	0.21	0.33	0.53	0.13	0.67	0.85	0.20	0.41	0.63
Invasive breast cancer	35	0.06	0.25	0.81	0.06	0.32	0.86	0.60	0.65	0.36	0.23	0.40	0.56
P value for trend		0.71			0.35			0.35			0.32

NOTE: Beta coefficients with P values <0.05 are presented in bold font. P values for trend are presented in italics.

↵^aMammographic density measures were square-root transformed.
↵^bTertiles of height and weight are presented.