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Table 2 Associations of reproductive variables with the percentage of different tissue types (log-transformed) in benign breast biopsy samples (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 86 − 0.26 (− 0.41; − 0.11) 0.04 (0.01; 0.08) − 0.34 (− 0.54; − 0.13) 0.01 (− 0.02; 0.05)
 Parous 880 Ref Ref Ref Ref
Breastfeeding, monthsc
 0 to < 1 361 Ref Ref Ref Ref
 1 to < 12 279 0.03 (− 0.07; 0.13) 0.02 (− 0.01; 0.04) − 0.06 (− 0.18; 0.07) 0.01 (− 0.01; 0.04)
 12 to < 24 119 0.08 (− 0.05; 0.22) 0.01 (− 0.03; 0.04) − 0.05 (− 0.22; 0.12) 0.01 (− 0.03; 0.04)
 ≥ 24 57 0.04 (− 0.15; 0.23) 0.02 (− 0.03; 0.08) − 0.30 (− 0.54; − 0.06) 0.03 (− 0.02; 0.07)
 p-trend 816 0.39 0.43 0.04 0.34
Parityd
 1 82 Ref Ref Ref Ref
 2 292 0.11 (− 0.05; 0.27) − 0.02 (− 0.06; 0.02) − 0.05 (− 0.25; 0.15) 0.01 (− 0.03; 0.05)
 3 269 0.12 (− 0.05; 0.28) − 0.03 (− 0.08; 0.01) 0.01 (− 0.19; 0.22) − 0.01(− 0.05; 0.03)
 ≥ 4 223 0.16 (− 0.02; 0.33) − 0.05 (− 0.10; − 0.00) 0.04 (− 0.18; 0.26) − 0.02(− 0.06; 0.03)
p-trend 866 0.13 0.02 0.32 0.17
Parity continuousd 866 0.03 (− 0.00; 0.07) − 0.01 (− 0.02; − 0.00) 0.01 (− 0.03; 0.06) − 0.01 (− 0.01; 0.00)
Age at first child’s birthe
 < 25 445 ref ref ref ref
 25–29 331 0.12 (0.03; 0.21) − 0.01 (− 0.03; 0.02) − 0.09 (− 0.20; 0.03) 0.01 (− 0.01; 0.03)
 ≥ 30 90 0.07 (− 0.08; 0.23) − 0.03 (− 0.07; 0.01) − 0.04 (− 0.23; 0.15) − 0.01 (− 0.05; 0.03)
 p-trend 866 0.13 0.16 0.44 0.85
Age at first birth continuous (per 5 years)e 866 0.04 (− 0.02; 0.11) − 0.01 (− 0.02; 0.01) − 0.03 (− 0.11; 0.05) − 1.8 × 10−3 (− 0.01; 0.02)
Age at menarchef
 < 12 176 − 0.09 (− 0.22; 0.04) − 0.01 (− 0.05; 0.02) 0.07 (− 0.12; 0.25) − 0.01 (− 0.05; 0.02)
 12 275 − 0.13 (− 0.24; − 0.01) − 0.04 (− 0.07; − 0.01) 0.10 (− 0.06; 0.26) − 0.05 (− 0.07; − 0.02)
 13 287 − 0.06 (− 0.17; 0.05) − 0.03 (− 0.06; − 0.00) − 0.01 (− 0.17; 0.15) − 0.03 (− 0.05; − 0.00)
 > 13 228 ref ref ref ref
 p-trend 966 0.07 0.23 0.24 0.11
Age at menarche continuous (per 5 years)f 966 0.15 (− 0.01, 0.30) 0.02 (− 0.02, 0.06) − 0.11 (− 0.33, 0.11) 0.03 (− 0.01, 0.06)
Time between menarche and age at first birth, continuous (per 5 years)g 866 0.02 (− 0.04; 0.08) − 0.01 (− 0.02; 0.01) − 0.01 (− 0.09; 0.06) − 1.7 × 10−3 (− 0.02; 0.01)
Time since the last pregnancy, continuous (per 5 years)c 839 − 0.05 (− 0.12; 0.02) − 0.02 (− 0.04 –3.0 × 10−3) 0.05 (− 0.03; 0.14) − 0.02 (− 0.04; − 3.0 × 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), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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, age at first child’s birth, a family history of breast cancer (yes/no), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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, age at menarche (< 12, 12, 13, > 13), a family history of breast cancer (yes/no), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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, age at menarche (< 12, 12, 13, > 13), a family history of breast cancer (yes/no), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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, a family history of breast cancer (yes/no), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), NHS cohort (NHSI, NHSII), and alcohol use (none, > 0 to < 5, ≥ 5 g/day)