| |
White women
|
African-American women
|
|---|
|
Controls
|
Triple-negative
|
Luminal A-like
|
Controls
|
Triple-negative
|
Luminal A-like
|
|---|
|
N
|
N
|
OR (95% CI)
|
N
|
OR (95% CI)
|
N
|
N
|
OR (95% CI)
|
N
|
OR (95% CI)
|
|---|
|
Younger (20–44 years)a
|
|
Duration of breastfeeding, months
|
|
Never
|
85
|
27
|
1.00
|
57
|
1.00
|
119
|
37
|
1.00
|
43
|
1.00
|
|
Ever
|
383
|
105
|
0.85 (0.49–1.49)
|
218
|
0.71 (0.46–1.11)
|
148
|
37
|
0.43 (0.22–0.83)
|
48
|
0.58 (0.32–1.06)
|
|
<6
|
136
|
43
|
0.94 (0.52–1.72)
|
72
|
0.70 (0.43–1.14)
|
73
|
26
|
0.67 (0.33–1.36)
|
25
|
0.64 (0.32–1.26)
|
|
≥6
|
247
|
62
|
0.76 (0.41–1.41)
|
146
|
0.73 (0.45–1.18)
|
75
|
11
|
0.18 (0.07–0.46)
|
23
|
0.50 (0.24–1.06)
|
|
Trend P value
| | |
0.34
| |
0.28
| | |
0.0004
| |
0.07
|
|
P value for homogeneity of trends
|
0.93
| | | | |
0.09
| |
|
Older (45–64 years)b
|
|
Duration of breastfeeding, months
|
|
Never
|
283
|
39
|
1.00
|
171
|
1.00
|
261
|
63
|
1.00
|
96
|
1.00
|
|
Ever
|
462
|
74
|
1.06 (0.65–1.72)
|
374
|
0.83 (0.63–1.10)
|
249
|
48
|
0.74 (0.47–1.17)
|
92
|
0.90 (0.62–1.30)
|
|
< 6
|
207
|
41
|
1.30 (0.78–2.19)
|
158
|
0.91 (0.67–1.25)
|
125
|
24
|
0.69 (0.39–1.21)
|
48
|
0.94 (0.60–1.46)
|
|
≥ 6
|
255
|
33
|
0.75 (0.41–1.38)
|
216
|
0.73 (0.53–1.02)
|
124
|
24
|
0.81 (0.46–1.43)
|
44
|
0.85 (0.54–1.35)
|
|
Trend P value
| | |
0.41
| |
0.07
| | |
0.35
| |
0.49
|
|
P value for homogeneity of trends
|
0.85
| | | | |
0.72
| |
- Triple negative = estrogen receptor (ER)–/progesterone receptor (PR)–/human epidermal growth factor receptor-2 (HER2)–, Luminal A-like = ER+ and/or PR+ plus HER2. Models in multivariate analysis included sub-study (the Women’s CARE Study or Women’s BCIS Study, Women’s LIFE Study), study site (Los Angeles, Detroit), reference age (in 5-year age categories), education (< high school, technical school or some college, college graduate), first-degree breast cancer family history (no, yes), body mass index (<25, 25–29, ≥30 kg/m2), lifetime recreational physical activity (inactive, ≤2.2, 2.3–6.6, 6.7–15.1, ≥15.2 annual metabolic energy equivalents, hour/week), alcohol intake (never, former, current), cigarette smoking status (never, former, current), age at menarche (≤12,13, ≥14 years), number of completed pregnancies (1, 2, ≥3), oral contraceptive use (never, <1, 1–4, 5–9, ≥10 years) and age at first completed pregnancy (≤20, 21–24, 25–29, ≥30 years). aAdditionally three white younger case participants who had missing information on breastfeeding were excluded. bAdditionally adjusted for a variable combining menopausal status and hormone therapy use (premenopausal; postmenopausal: never used hormone therapy, ever used hormone therapy; unknown menopausal status)
