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Table 3 Multivariable-adjusteda hazard ratios (HRs) and 95% confidence intervals for molecular breast cancer subtypes in relation to parity and breastfeeding: Nurses’ Health Study (1976–2012) and Nurses’ Health Study II (1989–2013)

From: Parity, breastfeeding, and breast cancer risk by hormone receptor status and molecular phenotype: results from the Nurses’ Health Studies

  Luminal A Luminal B HER2-enriched Basal-like Phet by subtype
  Cases PY HR (95%CI) Cases PY HR (95%CI) Cases PY HR (95%CI) Cases PY HR (95%CI)
Parity/breastfeeding
 Nulliparous 199 743,688 1 (ref.) 109 743,762 1 (ref.) 9 743,854 1 (ref.) 34 743,835 1 (ref.)  
 Parous women, never breastfed 613 1,361,275 1.00 (0.85–1.18) 269 1,361,572 0.82 (0.65–1.04) 62 1,361,777 2.09 (1.02–4.30) 121 1,361,712 1.34 (0.90–2.00) 0.04b
  1 child 89 210,499 1.07 (0.83–1.38) 48 210,527 1.11 (0.78–1.56) 13 210,562 3.35 (1.41–7.93) 14 210,562 1.08 (0.58–2.03) 0.03c
  2 children 228 517,884 1.05 (0.87–1.28) 92 518,005 0.78 (0.58–1.03) 29 518,065 2.81 (1.31–6.05) 45 518,050 1.40 (0.89–2.22)  
  ≥ 3 children 296 632,891 0.93 (0.77–1.12) 129 633,040 0.76 (0.58–1.00) 20 633,150 1.29 (0.57–2.90) 62 633,100 1.43 (0.92–2.23)  
 Parous women, ever breastfed 1091 3,187,450 0.87 (0.74–1.01) 556 3,187,935 0.80 (0.65–0.99) 115 3,188,338 1.90 (0.95–3.80) 186 3,188,280 0.96 (0.66–1.40)  
  1 child 92 314,469 0.98 (0.76–1.26) 51 314,504 0.97 (0.70–1.36) 9 314,536 1.94 (0.77–4.92) 16 314,532 0.99 (0.54–1.80)  
  2 children 340 1,168,513 0.87 (0.73–1.03) 174 1,168,664 0.77 (0.61–0.99) 26 1,168,794 1.43 (0.66–3.09) 55 1,168,780 0.84 (0.54–1.30)  
  ≥ 3 children 659 1,704,468 0.84 (0.71–0.99) 331 1,704,767 0.78 (0.62–0.98) 80 1,705,008 2.11 (1.03–4.29) 115 1,704,968 1.05 (0.70–1.57)  
  1. aAdjusted for age, height (< 1.60, 1.60 to < 1.65, 1.65 to < 1.70, 1.70 to < 1.75, 1.75+ meters), BMI at age 18 (< 20, 20–21.9, 22–23.9, 24–26.9, 27+ kg/m2), weight change since age 18 (continuous, kg), age at menarche (< 12, 12, 13, 14, 15+ years), menopausal status (premenopausal, postmenopausal or unknown), age at natural menopause (continuous), HT use (never, past, current E only, current E + P, current other), alcohol consumption (non-drinker, < 5, 5–10, 10–15, 15+ g/day), total physical activity (< 3, 3–9, 9–18, 18–27, 27+ MET-h/day), family history of breast cancer (yes/no), history of benign breast disease (yes/no), age at first birth (continuous, years)
  2. bPhet for nulliparous and parous ever vs. never breastfed
  3. cPhet for nulliparous and number of children by ever vs. never breastfed