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Table 2 Description of individuals with complete information

From: A genome-wide linkage study of mammographic density, a risk factor for breast cancer

  All sites Australia Northern California Ontario
Women, number 3,253 1,537 579 1,137
Age at mammogram, year 52.8 (8.7) 54.1 (8.9) 51.1 (8.3) 52.0 (8.3)
Self-reported ethnicity, n (%)     
Non-Hispanic white 2,843 (87.4) 1,495 (97.3) 255 (44.0) 1,093 (96.1)
Black 89 (2.7) 0 89 (15.5) 0
East Asian 127 (3.9) 0 119 (20.6) 8 (0.7)
Other/Mixed 189 (5.8) 38 (2.2) 116 (20.0) 35 (3.1)
Age at menarche, year 12.9 (1.5) 13.0 (1.6) 12.8 (1.5) 12.8 (1.5)
Pregnant ever, n (%) 2,889 (88.8) 1,402 (91.2) 496 (85.7) 991 (87.2)
Number of live births, n (%)     
0 489 (15.0) 187 (12.2) 123 (21.2) 179 (15.7)
1 314 (9.7) 115 (7.5) 88 (15.2) 111 (9.8)
2 1,165 (35.8) 534 (34.7) 185 (32.0) 446 (39.2)
3+ 1,285 (39.5) 701 (45.6) 183 (31.6) 401 (35.3)
Postmenopausal, n (%) 2,129 (65.5) 1,033 (67.2) 380 (65.6) 716 (63.0)
Past or current hormone therapy use, n (%) 1,248 (38.4) 572 (37.2) 262 (45.3) 414 (36.4)
Body mass index 26.1 (5.4) 26.2 (5.3) 26.4 (6.1) 25.9 (5.1)
Personal history of breast cancer, n (%) 601 (18.5) 84 (5.5) 221 (38.2) 296 (26.0)
PMD 30.3 (17.6) 28.1 (16.1) 33.4 (18.2) 31.6 (18.9)
  1. Risk factors are given as mean (SD) unless otherwise stated. PMD, percent mammographic density.