Table 1.

Characteristics of treated and untreated participants [mean (SD) or proportions where applicable]

CharacteristicsTreated (n = 167)Untreated (n = 142)P
Age (y), mean (SD)
    At interview48.4 (4.8)46.2 (4.1)<0.001
    At mammogram48.0 (4.7)45.8 (4.1)<0.001
Postmenopausal* (%)57 (34.1)25 (17.6)0.001
Age at menarche (y), mean (SD)12.8 (1.6)12.8 (1.4)0.86
Live births (%)
    036 (21.6)26 (18.3)0.48
    123 (13.8)11 (7.8)
    ≥2108 (64.7)105 (74)
Age at first live birth (y), mean (SD)30.0 (4.6)29.4 (4.5)0.25
Height (cm), mean (SD)178.4 (3.8)175.6 (4.7)<0.001
Weight (kg), mean (SD)78.4 (16.2)79.9 (15.7)0.40
BMI (kg/m2), mean (SD)24.6 (5.2)25.9 (4.9)0.030
Birthweight (kg),§ mean (SD)3.6 (0.51)3.5 (0.49)0.13
Birth length (cm), mean (SD)53.2 (2.5)52.9 (2.4)0.53
EMH-final height (cm), mean (SD)2.1 (2.8)−1.0 (3.2)<0.001
Fertility drugs (ever used; %)43 (25.8)18 (12.7)0.004
HRT
    Ever used (%)35 (21.0)15 (10.6)0.013
    Current use (%)22 (13.2)7 (4.9)0.013
    Total use (y), mean (SD)3.9 (6.2)2.6 (3.1)0.073
Hormonal contraceptive
    Ever used (%)161 (96.4)138 (97.2)0.70
    Current use (%)20 (12.0)22 (15.5)0.37
    Total use (y), mean (SD)10.1 (7.2)11.9 (6.7)0.028
Family history of breast cancer: first-degree relative (%)27 (16.2)19 (13.4)0.49
Smoking (%)
    Ever smoked88 (52.7)83 (58.4)0.31
    Currently smoke18 (10.8)17 (12.0)0.74
Alcohol use (%)
    Never or rarely drink24 (14.3)24 (16.9)0.24
    Occasionally (less than once a week)28 (16.8)25 (17.6)
    Once or twice a week33 (19.8)34 (23.9)
    ≥3 d/wk82 (49.1)59 (41.5)
Benign breast disease (%)37 (22.2)23 (16.2)0.19
Endometriosis** (%)30 (18.0)16 (11.3)0.10
Total breast area (cm2)
    Median (5th and 95th percentile range)102.6 (49.7-232.9)111.8 (57.4-236.0)
    Mean (SD)114.5 (57.2)123.9 (55.5)0.15
Dense area (cm2)
    Median (5th and 95th percentile range)26.4 (3.1-60.0)27.8 (4.7-77.6)
    Mean (SD)27.6 (17.6)32.8 (22.8)0.022
Nondense area (cm2)
    Median (5th and 95th percentile range)71.7 (18.5-226.9)69.2 (27.0-225.8)
    Mean (SD)87.0 (60.5)91.1 (59.8)0.55
Percent density (%)
    Median (5th and 95th percentile range)26.8 (2.2-67.1)28.2 (2.5-66.1)
    Mean (SD)29.5 (20.4)30.8 (19.6)0.58
  • *Women were defined as postmenopausal if the time since their last period was ≥52 weeks and (a) they had not started HRT before their periods ended or (b) they started HRT before their periods ended and they were ages ≥55 years.

  • Age at menarche: 1 missing.

  • P value for ever live birth.

  • §Birthweight: n = 72 treated and 112 untreated.

  • Birth length: n = 48 treated and 58 untreated.

  • EMH: n = 251.

  • **Endometriosis: 2 missing.