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. Author manuscript; available in PMC: 2008 Jul 3.
Published in final edited form as: Breast Cancer Res Treat. 2007 Jun 20;109(1):123–139. doi: 10.1007/s10549-007-9632-6

Table 3.

Case–control odds ratios comparing luminal A cases versus controls and basal-like cases versus controls

Risk factor Controls Luminal A
Basal-like
N N OR (95% CI) N OR (95% CI)
Age at menarchea
 ≥13 1,072 406 Referent 100 Referent
 <13 942 389 1.1 (0.9–1.3) 125 1.4 (1.1–1.9)
Parityb
 Nulliparous 230 132 Referent 26 Referent
 1 child 343 122 0.7 (0.5–1.0) 38 1.7 (0.9–3.0)
 2 670 259 0.7 (0.6–1.0) 79 1.8 (1.1–3.1)
 ≥3 779 283 0.7 (0.5–0.9) 82 1.9 (1.1–3.3)
Trend test P = 0.07 P = 0.04
Age at first full-term pregnancyb
 Nulliparous 230 132 Referent 26 Referent
 <26 1,354 477 0.7 (0.5–0.9) 159 1.9 (1.2–3.2)
 ≥26 435 184 0.9 (0.6–1.2) 39 1.5 (0.8–2.8)
Breastfeedingc
 Never 1,223 500 Referent 158 Referent
 Ever 799 296 0.9 (0.7–1.0) 67 0.7 (0.5–1.0)
Lifetime duration lactationc
 Never 1,223 500 Referent 158 Referent
 >0 to 3 months 280 92 0.7 (0.6–0.9) 27 0.9 (0.6–1.4)
 ≥4 516 204 0.9 (0.7–1.1) 40 0.7 (0.4–0.9)
Trend test P = 0.26 P = 0.03
Number of children breastfedc
 Never 1,223 500 Referent 158 Referent
 1 384 121 0.7 (0.6–0.9) 35 0.8 (0.6–1.2)
 ≥2 415 175 1.0 (0.8–1.2) 32 0.6 (0.4–0.9)
Trend test P = 0.33 P = 0.03
Ave. number months breastfeeding per childc
 Never 1,223 500 Referent 158 Referent
 0–3.9 480 172 0.8 (0.7–1.0) 42 0.8 (0.6–1.2)
 ≥4 316 124 0.9 (0.7–1.2) 25 0.6 (0.4–0.9)
Trend test P = 0.20 P = 0.03
Lactation suppressant usec
 Never 1,033 447 Referent 102 Referent
 Ever 989 349 0.9 (0.8–1.1) 123 1.5 (1.1–2.0)
Parity and lactationc
 Nulliparous 230 132 Referent 26 Referent
 1–2, never 625 232 0.7 (0.6–0.9) 81 1.8 (1.1–3.0)
 1–2, ever 388 149 0.7 (0.5–0.9) 36 1.1 (0.6–2.0)
 ≥3, never 368 136 0.7 (0.5–0.9) 51 1.9 (1.1–3.3)
 ≥3, ever 411 147 0.7 (0.5–0.9) 31 1.3 (0.7–2.3)
Parity and AFFTPc
 Nulliparous 230 132 Referent 26 Referent
 1–2, <26 653 221 0.6 (0.5–0.8) 82 1.7 (1.0–2.8)
 1–2, 26+ 360 160 0.8 (0.6–1.1) 34 1.2 (0.7–2.2)
 ≥3, <26 701 256 0.7 (0.5–0.9) 77 1.6 (1.0–2.8)
 ≥3, 26+ 75 24 0.6 (0.3–1.0) 5 1.2 (0.4–3.5)
BMI (kg/m2)d
Overall
 <25 615 288 Referent 64 Referent
 25–29 609 208 0.7 (0.6–0.9) 66 1.0 (0.7–1.5)
 ≥30 751 277 0.8 (0.6–1.0) 88 0.8 (0.6–1.2)
Trend test P = 0.04 P = 0.30
Premenopausal
 <25 292 138 Referent 34 Referent
 25–29 233 75 0.7 (0.5–1.0) 35 1.1 (0.7–1.9)
 ≥30 318 105 0.7 (0.5–1.0) 50 1.0 (0.6–1.8)
Trend test P = 0.08 P = 0.96
Postmenopausal
 <25 323 150 Referent 30 Referent
 25–29 376 133 0.8 (0.6–1.0) 31 0.8 (0.5–1.4)
 ≥30 433 172 0.8 (0.6–1.1) 38 0.6 (0.3–1.1)
Trend test P = 0.22 P = 0.10
WHRe
Overall
 <0.77 615 210 Referent 40 Referent
 0.77–0.83 646 268 1.3 (1.1–1.7) 89 2.3 (1.5–3.5)
 ≥0.84 732 306 1.5 (1.1–1.9) 91 2.3 (1.4–3.6)
Trend test P = 0.005 P = 0.002
Premenopausal
 <0.77 324 122 Referent 25 Referent
 0.77–0.83 277 113 1.3 (0.9–1.8) 56 2.6 (1.5–4.5)
 ≥0.84 253 86 1.2 (0.8–1.8) 41 1.8 (1.0–3.4)
Trend test P = 0.41 P = 0.07
Postmenopausal
 <0.77 291 88 Referent 15 Referent
 0.77–0.83 369 155 1.5 (1.1–2.1) 33 1.8 (0.9–3.6)
 ≥0.84 479 220 1.8 (1.3–2.6) 50 2.7 (1.3–5.4)
Trend test P = 0.002 P = 0.006
a

Adjusted for offsets, age (continuous), race (African-American, white), menopausal status (pre-, postmenopausal), family history (yes, no), alcohol use (ever, never), smoking duration (never, ≤10, 11–20, >20 years), oral contraceptive use (ever, never), parity (nulliparous, 1–2,3+), breastfeeding (ever, never)

b

Adjusted for offsets, age, race, menopausal status, family history, alcohol use, smoking duration, oral contraceptive use, age at menarche (<13, 13+), breastfeeding

c

Adjusted for offsets, age, race, menopausal status, family history, alcohol use, smoking duration, oral contraceptive use, age at menarche

d

Adjusted for offsets, age, race, menopausal status (overall analysis), family history, alcohol use, smoking duration, oral contraceptive use, age at menarche, parity breastfeeding

e

Adjusted for offsets, age, race, menopausal status (overall analysis), family history, alcohol use, smoking duration, oral contraceptive use, age at menarche, parity breastfeeding and BMI (continuous)