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Table 1 Demographic and hormone-related risk factors

From: Hormone-related risk factors for breast cancer in women under age 50 years by estrogen and progesterone receptor status: results from a case–control and a case–case comparison

Variables Cases by availability of ER/PR information Controls
  Cases with known receptor status Cases with borderline positive/undecided status Cases without information p for comparison across the three case groups  
Number of subjects 1,366 (79.2%) 83 (4.8%) 276 (16.0%)   440
Mean age at reference date (SD), years 42.5 (5.4) 42.8 (5.2) 44.0 (4.6) 0.0001a,b 42.6 (4.9)
Race      
   White 1,206 (88.3%) 77 (92.8%) 238 (86.2%)   405 (92.0%)
   African-American 160 (11.7%) 6 (7.2%) 38 (13.8%) 0.26c 35 (8.0%)
Education      
   High school or lower 262 (19.2%) 19 (22.9%) 76 (27.5%)   60 (13.6%)
   Technical school or some college 489 (35.8%) 28 (33.7%) 103 (37.3%)   150 (34.1%)
   College graduate 615 (45.0%) 36 (43.4%) 97 (35.2%) 0.01c,d 230 (52.3%)
First-degree breast cancer family history      
   No 1,091 (79.9%) 63 (75.9%) 224 (81.1%)   388 (88.2%)
   Yes 229 (16.7%) 19 (22.9%) 46 (16.7%)   41 (9.3%)
   Unknowne 46 (3.4%) 1 (1.2%) 6 (2.2%) 0.39c 11 (2.5%)
Mean age at menarche (SD), years 12.4 (1.5) 12.6 (1.7) 12.4 (1.4) 0.51a 12.7 (1.5)
Ever had a full-term (>26-week) pregnancy 66.6% 74.7% 68.5% 0.28c 71.6%
Mean number of full-term pregnancies (SD) 2.1 (1.0) 2.1 (1.1) 2.1 (0.9) 0.92a 2.2 (1.1)
Mean age at first full-term pregnancy (SD) 26.7 (6.4) 26.2 (6.2) 24.9 (5.8) 0.002a,b 27.1 (6.2)
Ever breastfed among parous women 80.4% 77.4% 70.9% 0.01c,d 87.9%
Mean duration of breastfeeding (all pregnancies) among those who breastfed (SD), months 14.2 (16.3) 13.7 (13.6) 12.6 (14.6) 0.56a 16.6 (17.3)
Mean BMI 1 year before reference date (SD), kg/m2 25.8 (6.1) 26.2 (6.4) 26.6 (6.5) 0.12a 25.7 (6.4)
Ever used COC 85.9% 84.3% 85.9% 0.92c 89.3%
Mean duration of COC use among users (SD), years 6.9 (6.3) 5.8 (6.6) 6.4 (6.4) 0.23a 6.7 (6.2)
Alcohol drinking status during reference age      
   Never 428 (31.3%) 34 (41.0%) 96 (37.8%)   141 (32.1%)
   Former 259 (19.0%) 16 (19.3%) 53 (19.2%)   90 (20.5%)
   Current 679 (49.7%) 33 (39.7%) 127 (46.0%) 0.30c 209 (47.5%)
Alcohol drinking status in recent 5-year period      
   No 428 (31.3%) 34 (41.0%) 96 (34.8%)   141 (32.1%)
   Yes 759 (55.6%) 40 (48.2%) 137 (49.6%)   228 (51.8%)
   Yes, but not in the five year period 179 (13.1%) 9 (10.8%) 43 (15.6%) 0.17c 71 (16.1%)
Mean number of alcoholic drinks per week in recent 5 years for drinkers (SD) 6.6 (20.1) 4.9 (6.1) 6.0 (8.4) 0.80a 4.6 (9.1)
  1. Results are for 1,725 case patients and 440 control subjects. BMI, body mass index; COC, combined oral contraceptive; ER/PR, estrogen receptor and progesterone receptor; SD, standard deviation. a F test. bBonferroni t tests for pairwise comparisons: p values for cases with complete ER/PR information versus cases without ER/PR information ≤ 0.001, and p values for the other comparisons ≥ 0.20. cPearson χ2 test. dPearson χ2 tests for pairwise comparisons: p values for cases with complete ER/PR information versus cases without ER/PR information ≤ 0.004, and p values for the other comparisons ≥ 0.32. eUnknown category was excluded from Pearson χ2 tests.