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Table 1 Baseline characteristics of the participants and their association with mammographic percent density

From: Mammographic density and markers of socioeconomic status: a cross-sectional study

Participant baseline characteristics n Mean SD  
Age at mammography (yrs) 487 48.6 1.6  
Weight (kg) 487 67.6 12.9  
Age at menarche (yrs) 194 13.1 1.5  
   n % Median PD (25 th , 75 th ) 1
Smoking 487    
   Never   273 56 26.7 (13.7, 43.5)
   Ex smoker   152 31 29.5 (14.1, 46.7)
   Current   62 13 27.2 (10.5, 42.7)
Height (m) 487    
   <1.60   158 32 24.9 (13.3, 43.8)
   1.60-1.64   137 28 26.9 (12.3, 43.5)
   1.65-1.69   110 23 28.6 (15.4, 43.4)
   ≥ 1.7   82 17 31.1 (18.2, 43.0)
BMI (kg/m2) 487    
   <22   115 24 46.0 (32.1, 61.6)
   22-24.9   145 30 31.5 (19.5, 43.1)
   25-27.9   115 24 22.1 (11.6, 37.4)
   ≥ 28   112 23 9.5 (4.0, 21.6)
Number of full-term pregnancies 487    
   0   63 13 32.9 (10.4, 53.6)
   1-2   297 61 28.7 (14.2, 45.6)
   3+   127 26 23.5 (13.8, 39.0)
Age at first full-term pregnancy2 424    
   <24 years   140 33 22.7 (12.0, 37.8)
   24-28.9 years   160 38 26.3 (14.6, 42.4)
   ≥ 29 years   124 29 31.6 (16.1, 49.7)
Family history of breast cancer 487    
   Yes   53 11 28.6 (15.8, 46.5)
   No   434 89 27.5 (13.7, 43.4)
Lifetime breast feeding2,3 326    
   Never   55 17 21.6 (9.4, 37.9)
   1-6 months   90 28 28.4 (13.3, 39.7)
   7-12 months   60 18 30.0 (15.5, 52.6)
   ≥ 13 months   121 37 32.1 (16.4, 47.2)
  1. 1 Median percent mammographic density (%) with 25th and 75th percentiles
  2. 2 Among parous women only
  3. 3 Available only for the 369 women who completed the follow-up questionnaire, 326 of whom were parous