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Table 1 Characteristics of the Study Population*

From: Breast density and polymorphisms in genes coding for CYP1A2 and COMT: the Multiethnic Cohort

Characteristic Cases Controls All
Number of women 325 250 575
Ethnicity    
   Caucasian 112 (34.5) 74 (29.6) 186 (32.4)
   Japanese 168 (51.7) 101 (40.4) 269 (46.8)
   Native Hawaiian 43 (13.2) 75 (30.0) 118 (20.5)
Number of mammograms 3.4 ± 1.9 2.5 ± 1.2 3.0 ± 1.7
Age at first mammogram (years) 57.4 ± 8.9 56.8 ± 9.9 57.1 ± 9.3
Percent density at first mammogram (%) 36.7 ± 22.8 30.6 ± 23.3 34.0 ± 23.2
Time between first and last mammogram (years) 5.2 ± 3.8 4.2 ± 3.8 4.7 ± 3.8
Postmenopausal at time of first mammogram 233 (71.7) 153 (61.2) 386 (67.1)
Hormone replacement therapy by mammogram    
   None 472 (42.5) 290 (47.2) 762 (44.3)
   Estrogen only 282 (25.5) 207 (33.7) 489 (28.4)
   Estrogen plus progestin 354 (32.0) 117 (19.1) 471 (27.3)
Overweight/obese (BMI ≥ 25 kg/m2) 121 (37.2) 113 (45.2) 234 (40.7)
Family history of breast cancer 56 (17.2) 31 (12.4) 87 (15.1)
Age at menarche younger than 13 years 194 (59.7) 136 (54.4) 330 (57.4)
Age at first live birth older than 30 years 29 (8.9) 26 (10.4) 55 (9.6)
Nulliparity 43 (13.2) 31 (12.4) 74 (12.9)
Parity 3+ children 72 (22.2) 53 (21.2) 125 (21.7)
  1. * Mean ± SD are given for continuous measures, counts and percentages for other variables.