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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: Epidemiology. 2019 May;30(3):449–457. doi: 10.1097/EDE.0000000000000981

Table 3.

Joint Associations of Breast-feeding, Parity, and Age at First Birth on Overall Breast Cancer Risk among U.S. Hispanic and Mexican Women

U.S. Hispanic and Mexican Women Combined
Cases
N=2,703		 Controls
N=3,254
N N OR 95% CIa
Parityb by duration of breast-feeding (months)c
 1 birth
  No breast-feeding 183 124 1.0
  1–12 months breast-feeding 191 168 0.74 0.54–1.02
  ≥13 months breast-feeding 26 24 0.65 0.35–1.21
 2–3 births
  No breast-feeding 432 436 0.72 0.54–0.95
  1–12 months breast-feeding 784 818 0.68 0.52–0.88
  ≥13 months breast-feeding 246 324 0.54 0.40–0.73
 ≥4 births
  No breast-feeding 168 216 0.65 0.47–0.89
  1–12 months breast-feeding 307 457 0.53 0.40–0.72
  ≥13 months breast-feeding 366 687 0.49 0.37–0.65
P interaction = 0.56
Age at first live birth (years) by duration of breast-feeding (months)d
 <20 years
  ≥13 months breast-feeding 245 441 1.0
  1–12 months breast-feeding 327 447 1.05 0.84–1.32
  No breast-feeding 183 208 1.26 0.96–1.65
 20–29 years
  ≥13 months breast-feeding 326 526 1.04 0.84–1.30
  1–12 months breast-feeding 776 854 1.26 1.02–1.55
  No breast-feeding 470 482 1.38 1.11–1.74
 ≥30 years
  ≥13 months breast-feeding 67 68 1.23 0.83–1.85
  1–12 months breast-feeding 179 142 1.55 1.14–2.11
  No breast-feeding 130 86 1.88 1.32–2.67
P interaction = 0.47

Abbreviations: 4-CBCS, 4-Corners Breast Cancer Study; HR+, hormone receptor positive (estrogen receptor positive and/or progesterone receptor positive); MBCS, Mexico Breast Cancer Study; NC-BCFR, Northern California Breast Cancer Family Registry; SFBCS, San Francisco Bay Area Breast Cancer Study.

a

Odds ratios and 95% confidence intervals, adjusted for age (years; continuous), study (SFBCS, NC-BCFR, 4-CBCS,MCBS), education (less than high school, high school graduate, post high school education), family history of breast cancer in first-degree relatives (no, yes), age at menarche (<12, 12, 13, ≥14 years), hormonal contraception use (never, former, current), menopausal status and hormone therapy use (premenopausal, postmenopausal never used HT, postmenopausal past HT use, postmenopausal current HT use, menopausal status unknown), average daily alcohol consumption (0, 0.1–4.9, 5–9.9, ≥10 grams), and body mass index in reference year (<25.0, 25.0–29.9, ≥30.0 kg/m2).

b

Number of live births.

c

Adjusted additionally for age at first live birth.

d

Adjusted additionally for parity