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Table 3 Associations of reproductive variables with the percentage of different tissue types (log-transformed) in benign breast biopsy samples of premenopausal women (β coefficients and 95% confidence intervals)

From: Associations of reproductive breast cancer risk factors with breast tissue composition

Reproductive factor

Number

Tissue type

% epithelial

% stroma

% fat

% fibroglandulara

Nulliparityb

 Nulliparous

61

− 0.22 (− 0.38; − 0.06)

0.06 (0.02; 0.10)

− 0.32 (− 0.56; − 0.08)

0.03 (− 0.01; 0.06)

 Parous

540

Ref

Ref

Ref

Ref

Breastfeeding, monthsc

 0 to < 1

210

Ref

Ref

Ref

Ref

 1 to < 12

162

− 0.06 (− 0.18; 0.06)

0.04 (0.01; 0.07)

− 0.11 (− 0.28; 0.06)

0.03 (− 0.00; 0.05)

 12 to < 24

92

− 0.02 (− 0.17; 0.13)

0.01 (− 0.03; 0.06)

− 0.02 (− 0.24; 0.19)

0.00 (− 0.03; 0.04)

 ≥ 24

47

− 0.09 (− 0.30; 0.11)

0.04 (− 0.02; 0.09)

− 0.18 (− 0.48; 0.11)

0.02 (− 0.02; 0.07)

 p-trend

511

0.53

0.33

0.39

0.57

Parityd

 1

62

Ref

Ref

Ref

Ref

 2

190

0.27 (0.10; 0.44)

− 0.02 ( − 0.07; 0.03)

− 0.17 (− 0.42; 0.07)

0.02 (− 0.02; 0.06)

 3

167

0.25 (0.08; 0.43)

− 0.04 (− 0.09; 0.01)

− 0.03 (− 0.29; 0.22)

− 0.00 (− 0.04; 0.04)

 ≥ 4

108

0.34 (0.14; 0.53)

− 0.06 (− 0.11; − 0.00)

0.03 (− 0.25; 0.30)

− 0.01 (− 0.05; 0.04)

 p-trend

527

0.01

0.02

0.25

0.23

Parity continuousd

527

0.07 (0.02; 0.11)

− 0.02 (− 0.03; − 0.00)

0.03 (− 0.03; 0.10)

− 0.01 (− 0.02; 0.00)

Age at first child’s birthe

 < 25

263

Ref

Ref

Ref

Ref

 25–29

205

0.20 (0.10; 0.31)

− 0.01 (− 0.04; 0.02)

− 0.19 (− 0.34; − 0.03)

0.02 (− 0.01; 0.04)

 ≥ 30

59

0.23 (0.06; 0.40)

− 0.05 (− 0.10; − 0.00)

0.01 (− 0.24; 0.26)

− 0.01 (− 0.05; 0.03)

 p-trend

527

< 0.01

0.05

0.58

0.99

Age at first birth continuous (per 5 years)e

527

0.10 (0.03; 0.17)

− 0.01 (− 0.03; 0.01)

− 0.04 (− 0.14; 0.06)

4.5 × 10−3 (− 0.01; 0.02)

Age at menarchef

 < 12

115

− 0.10 (− 0.25; 0.06)

− 0.01 (− 0.05; 0.03)

0.10 (− 0.13; 0.33)

− 0.02 (− 0.05; 0.02)

 12

174

− 0.14 (− 0.28; − 0.00)

− 0.03 (− 0.06; 0.01)

0.07 (− 0.14; 0.28)

− 0.03 (− 0.07; − 0.00)

 13

187

− 0.01 (− 0.14; 0.13)

− 0.02 (− 0.05; 0.02)

− 0.02 (− 0.22; 0.18)

− 0.01 (− 0.04; 0.02)

 > 13

125

Ref

Ref

Ref

Ref

 p-trend

601

0.06

0.61

0.24

0.14

Age at menarche continuous (per 5 years)f

601

0.16 (− 0.02, 0.33)

0.01 (− 0.04, 0.05)

− 0.13 (− 0.40, 0.13)

0.03 (− 0.02, 0.07)

Time between menarche and age at first birth, continuous (per 5 years)g

527

0.07 (− 8.0 × 10−3; 0.14)

− 0.01 (− 0.03; 0.01)

− 0.01 (− 0.11; 0.09)

− 9.0 × 10−3 (− 0.02; 0.02)

Time since the last pregnancy, continuous (per 5 years)c

501

− 0.04 (− 0.12; 0.05)

− 0.02 (− 0.04; 3.8 × 10−3)

0.07 (− 0.04; 0.19)

− 0.02 (− 0.04; 2.1 × 10−3)

  1. aFibroglandular tissue represents combined epithelium and stroma
  2. bAdjusted for age (continuous), BMI (continuous), age at menarche (< 12, 12, 13, > 13), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
  3. cAmong parous women only: adjusted for age (continuous), BMI (continuous), age at menarche (< 12, 12, 13, > 13), parity (1, 2, 3, and ≥4 children), age at first child’s birth (<25, 25-29, and ≥30 years), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
  4. dAmong parous women only: adjusted for age (continuous), BMI (continuous), age at first birth (<25, 25-29, and ≥30 years), age at menarche (< 12, 12, 13, > 13), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
  5. eAmong parous women only: adjusted for age (continuous), BMI (continuous), parity (1, 2, 3, and ≥4 children), age at menarche (< 12, 12, 13, > 13), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
  6. fAdjusted for age (continuous), BMI (continuous), parous status (nulliparous, parous), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
  7. gAmong parous women only: adjusted for age (continuous), BMI (continuous), parity (continuous), a family history of breast cancer (yes/no), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥5 g/day)
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Breast Cancer Research

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