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Table 3 Adjusted mean mammographic density measures according to reproductive and hormonal exposures among postmenopausal women

From: Predictors of mammographic density among women with a strong family history of breast cancer

   Postmenopausal women (n = 59)
  Percent Density (%)   Dense Area (cm2)   Non-Dense Area (cm2)
n Mean1 PD 95% CI1 P 1 n Mean1 DA 95% CI1 P 1 n Mean1 NDA 95% CI1 P 1
Age at menarche
 <13 years 21 14.3 8.7-21.2   18 18.0 10.8-27.0   18 121.6 92.3-154.9  
 ≥13 years 38 13.8 8.6-20.2 0.85 37 21.7 14.2-30.8 0.36 37 133.0 104.3-165.3 0.44
Parity
 Nulliparous 13 17.4 10.3-26.2   11 24.9 15.1-37.1   11 120.0 86.8-158.6  
 Parous 46 13.5 8.6-19.4 0.24 44 19.4 12.7-27.5 0.25 44 128.1 101.4-158.0 0.63
Total live births2
 1 6 21.3 11.7-33.8 ref 6 29.4 17.8-44.0 ref 6 95.1 59.5-139.1 ref
 2 22 12.9 7.0-20.4 0.09 20 19.5 12.0-28.9 0.11 20 143.0 106.9-184.3 0.04
 ≥3 18 12.8 6.4-21.5 0.11 18 20.9 12.3-31.6 0.19 18 146.4 106.4-192.9 0.04
Breastfeeding2
 Never 10 14.1 6.3-25.0   10 26.4 15.2-40.6   10 154.9 106.5-212.4  
 Ever 35 14.2 8.3-21.8 0.97 34 20.9 13.5-29.8 0.29 34 129.6 97.0-166.8 0.25
Breastfeeding duration2
 <11 months 26 12.9 6.9-20.8   24 20.9 12.8-31.1   24 148.8 110.8-192.5  
 ≥11 months 20 15.8 8.9-24.7 0.41 20 22.7 14.2-33.3 0.69 20 119.8 85.8-159.4 0.12
OC use
 Never 5 9.0 2.6-19.3   4 16.4 5.5-33.2   4 149.4 94.9-216.2  
 Ever 53 13.9 9.2-19.7 0.24 50 20.1 13.4-28.1 0.59 50 128.9 103.3-157.3 0.45
Duration of OC use
 <9 years 26 14.6 9.0-21.5   26 19.9 12.4-29.2   26 120.5 93.5-151.0  
 ≥9 years 27 12.9 7.6-19.6 0.55 24 20.1 12.3-29.8 0.95 24 140.6 110.3-174.6 0.16
HRT use
 Never 43 13.7 8.7-19.7 ref 39 19.9 13.1-28.1 ref 39 133.0 106.5-162.5 ref
 Former 9 14.8 7.2-25.0 0.77 9 19.1 9.4-32.1 0.88 9 100.4 66.3-141.5 0.08
 Current 7 16.1 7.4-28.2 0.60 7 24.0 11.7-40.8 0.52 7 123.8 80.7-176.1 0.68
  1. 1Adjusted least-square means, 95% confidence intervals, and P-values are from analyses using square root-transformed mammographic density measures. The adjusted least-square means and 95% confidence intervals were back-transformed
  2. 2Among parous women only
  3. All models were adjusted for age (continuous) and BMI (continuous) at the time of mammogram, parity (continuous), and mammogram modality (digital image, film scanned by study team, film scanned by imaging centre).The parity (total live births) and breastfeeding models were additionally adjusted for age at first birth (continuous). OC, oral contraceptives. HRT, hormone replacement therapy