. Author manuscript; available in PMC: 2023 Dec 1.

Published in final edited form as: Cancer Prev Res (Phila). 2023 Jun 1;16(6):353–361. doi: 10.1158/1940-6207.CAPR-22-0482

Table 4.

Associations of breastfeeding duration with mammographic breast density measures by menopause status, race and BMI among parous women^a

		Volumetric Percent Density		Dense Volume (cm³)		Non-dense Volume (cm³)

	N	10^β (95%CI)	P trend	10^β (95%CI)	P trend	10^β (95%CI)	P trend

Menopausal status

*Premenopausal* ^b			0.16		0.23		0.02
Parous never breastfed	157	Reference		Reference		Reference
0–6 months	63	1.04 (0.90, 1.19)		1.10 (0.96, 1.27)		1.09 (0.94, 1.25)
7–12 months	46	1.15 (0.98, 1.35)		1.00 (0.85, 1.17)		0.88 (0.75, 1.03)
>12 months	180	1.07 (0.96, 1.20)		0.95 (0.85, 1.06)		0.89 (0.80, 1.00)

*Postmenopausal* ^b			0.49		0.98		0.68
Parous never breastfed	132	Reference		Reference		Reference
0–6 months	52	0.94 (0.82, 1.08)		0.86 (0.67, 1.11)		0.92 (0.71, 1.18)
7–12 months	45	1.10 (0.95, 1.28)		1.04 (0.80, 1.37)		0.92 (0.70, 1.21)
>12 months	61	1.02 (0.89, 1.16)		0.97 (0.75, 1.24)		0.96 (0.74, 1.23)
P-interaction		0.52		0.20		0.31

Race

*Non-Hispanic white* ^c			0.50		0.45		0.31
Parous never breastfed	140	Reference		Reference		Reference
0–6 months	73	0.93 (0.81, 1.07)		0.97 (0.82, 1.16)		1.07 (0.90, 1.29)
7–12 months	66	1.09 (0.94, 1.26)		1.02 (0.85, 1.23)		0.94 (0.78, 1.14)
>12 months	190	1.01 (0.91, 1.13)		0.94 (0.82, 1.08)		0.95 (0.82, 1.10)

*Non-Hispanic black* ^c			0.04		0.87		0.18
Parous never breastfed	144	Reference		Reference		Reference
0–6 months	38	1.10 (0.96, 1.27)		1.00 (0.81, 1.23)		0.89 (0.72, 1.11)
7–12 months	20	1.12 (0.93, 1.33)		1.11 (0.84, 1.46)		0.99 (0.75, 1.30)
>12 months	34	1.14 (0.99, 1.33)		0.99 (0.79, 1.24)		0.85 (0.67, 1.06)
P-interaction		0.42		0.91		0.70

BMI

*BMI<25* ^d			0.12		0.34		0.56
Parous never breastfed	49	Reference		Reference		Reference
0–6 months	28	0.91 (0.70, 1.17)		1.23 (0.92, 1.65)		1.38 (0.99, 1.91)
7–12 months	30	1.20 (0.92, 1.56)		1.44 (1.07, 1.94)		1.17 (0.84, 1.64)
>12 months	96	1.12 (0.92, 1.38)		1.15 (0.91, 1.44)		1.00 (0.77, 1.29)

*BMI ≥25* ^d			0.18		0.13		0.04
Parous never breastfed	240	Reference		Reference		Reference
0–6 months	87	1.10 (0.98, 1.23)		0.93 (0.81, 1.08)		0.86 (0.73, 1.01)
7–12 months	61	1.13 (0.99, 1.29)		0.94 (0.80, 1.12)		0.84 (0.70, 1.01)
>12 months	145	1.06 (0.96, 1.17)		0.90 (0.79, 1.03)		0.87 (0.76, 1.00)
P-interaction		0.09		0.12		0.10

^a.

Mammographic breast density measures were log10 transformed due to the skewed distribution. Coefficients was back-transformed. CI = confidence intervals, MBD= mammographic breast density, BMI=body mass index. Bold indicates statistical significance (p<0.05), some CI may not appear significant due to rounding.

^b.

Models were adjusted for age (continuous), age at menarche (continuous), BMI (continuous), race (non-Hispanic white, non-Hispanic black, other), and family history of breast cancer (yes, no).

^c.

Models were adjusted for age (continuous), age at menarche (continuous), BMI (continuous), and family history of breast cancer (yes, no). Other races were excluded from the interaction analysis because of the small sample size

^d.

Models were adjusted for age (continuous), age at menarche (continuous), race (non-Hispanic white, non-Hispanic black, other), and family history of breast cancer (yes, no).