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Table 1 Characteristics of 297 cases and 1149 controls

From: Case-control study of mammographic density and breast cancer risk using processed digital mammograms

  Cases Controls
N = 297 % N = 1149 %
Age at mammogram
 Mean (SD) 63.79 7.21 63.95 7.00
 Categories:
  40–49 years 9 3.0 % 33 2.9 %
  50–59 years 67 22.6 % 238 20.7 %
  60–69 years 149 50.2 % 600 52.2 %
  70+ years 72 24.2 % 278 24.2 %
Body mass index (kg/m2)
 Mean (SD) 28.71 6.88 27.48 5.88
 Categories:
  24 or less 97 32.7 % 471 41.0 %
  25–29 99 33.3 % 347 30.2 %
  30–34 53 17.8 % 213 18.5 %
  35–39 22 7.4 % 71 6.2 %
  40+ 26 8.8 % 47 4.1 %
First-degree family history of breast cancer
 No 257 86.5 % 1058 92.1 %
 Yes 40 13.5 % 91 7.9 %
Use of postmenopausal hormonesa
 None 237 79.8 % 939 81.7 %
 Estrogen alone 28 9.4 % 106 9.2 %
 Estrogen + progestin 32 10.8 % 104 9.1 %
Parity
 Nulliparous 18 6.1 % 65 5.7 %
 Parous 229 77.1 % 916 79.7 %
 Missing 50 16.8 % 168 14.6 %
Percent densityb
 Mean (SD) 22.00 13.81 19.51 14.77
 Quintiles:
  Q1: 6.08 or less 40 13.5 % 229 19.9 %
  Q2: 6.09–11.94 49 16.5 % 230 20.0 %
  Q3: 11.95–20.04 60 20.2 % 230 20.0 %
  Q4: 20.05–31.56 69 23.2 % 230 20.0 %
  Q5: 31.57+ 79 26.6 % 230 20.0 %
Area of densityb
 Mean (SD) 32.66 20.13 26.33 17.47
 Quintiles:
  Q1: 11.95 or less 30 10.1 % 229 19.9 %
  Q2: 11.96–19.09 45 15.2 % 230 20.0 %
  Q3: 19.10–26.96 66 22.2 % 230 20.0 %
  Q4: 26.97–37.78 68 22.9 % 230 20.0 %
  Q5: 37.79+ 88 29.6 % 230 20.0 %
Total breast area
 Mean (SD) 175.92 81.23 167.67 74.01
  1. aWithin 2 years prior to mammogram date
  2. bMeasures are untransformed. Quintiles calculated from distribution of controls