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Table 1 Characteristics of the study population by disease status

From: The association of mammographic density with ductal carcinoma in situof the breast: the Multiethnic Cohort

Covariate Invasive breast cancer Breast DCIS Controls P valuea
Sample size 482 119 667 -
Ethnicity (%)     0.19b
   Hawaiian 14.3 8.4 24.3  
   Japanese 46.5 55.5 43.8  
   Caucasian 32.6 28.6 28.0  
   Other 6.6 7.6 3.9  
Age at diagnosis (years) 63.5 62.9 N/A 0.50b
Age at recruitment (years) 60.0 59.6 56.7 0.58b
Mean age at all mammograms (years) 59.8 59.1 59.7 0.70
Body mass index (kg/m2) 25.2 24.5 25.7 0.07
Time from first mammogram to diagnosis (years) 6.2 6.7 N/A 0.17b
Family history of breast cancer (%) 16.8 16.8 12.0 0.05
Age at first birth (years) 25.0 25.1 24.7 0.65
Age at menarche (years) 13.1 12.9 13.1 0.47
Parous (%) 84.5 83.9 88.5 0.10
Number of children 2.4 2.2 2.6 0.02
Postmenopausal (%) 86.3 89.9 77.7 <0.0001
Ever HRT use (%) 67.2 73.9 69.3 0.01
Number of mammograms 3.2c 3.4c 2.4c <0.0001
Breast percent densityd 36.5 38.2 29.4 <0.0001
Breast dense aread (cm2) 36.7 34.9 28.7 <0.0001
Total breast aread (cm2) 114.5 106.9 118.9 0.08
  1. Unless otherwise indicated, mean values are given. aP ascertained from t test or χ2 test, as appropriate. bCompares only invasive breast cancer and breast DCIS cases. All other comparisons are of invasive breast cancer cases, breast DCIS cases, and controls. cThe range for number of mammograms is 11, 10, and 7 for invasive breast cancer, breast DCIS, and controls, respectively. dAdjusted for age at recruitment. DCIS, ductal carcinoma in situ; HRT, hormone replacement therapy.