Table 1.

Characteristics of breast cancer cases and controls

CharacteristicCase n (%)*,
Control n (%)*,
n = 891n = 878
Age at reference date (y)
    65-69278 (31.2)278 (31.7)
    70-74613 (68.8)600 (68.3)
Age at menopause (y)
    <3974 (9.6)98 (11.2)
    40-44115 (14.9)130 (14.8)
    45-49233 (30.1)229 (26.1)
    50-54257 (33.2)239 (27.2)
    ≥5595 (12.3)103 (11.7)
    Missing data11779
Age at first full-term pregnancy (y)
    <30720 (81.1)726 (82.8)
    ≥30168 (18.9)151 (17.2)
    Missing data31
Cause of menopause
    Natural menopause508 (57.9)519 (59.9)
    Induced menopause122 (13.9)124 (14.3)
    Simple hysterectomy207 (23.6)198 (22.8)
    Other41 (4.7)26 (3.0)
    Missing data1311
BMI quartiles
    16.00-22.96169 (19.5)211 (24.8)
    22.97-26.01221 (25.6)213 (25.1)
    26.02-30.11244 (28.2)211 (24.8)
    30.12-48.70231 (26.7)214 (25.2)
    Missing data2629
    Mean BMI27.5 (5.7)26.9 (5.4)
EPT
    Never use648 (73.0)697 (79.8)
    <60 mo of use80 (9.0)80 (9.2)
    ≥60 mo of use160 (18.0)96 (11.0)
    Missing data35
ET
    Never use407 (46.1)412 (47.2)
    <60 mo of use157 (17.8)176 (20.2)
    ≥60 mo of use319 (36.1)284 (32.6)
    Missing data86
Race
    Caucasian854 (95.9)814 (92.7)
    African American11 (1.2)27 (3.1)
    Asian17 (1.9)21 (2.4)
    Other/unknown9 (1.0)16 (1.8)
  • Abbreviation: BMI, body mass index.

  • * With the exception of mean body mass index: mean (SD).

  • Some percentages do not sum to 100% due to rounding.

  • Using data imputed from hormone therapy use and bilateral oophorectomy status.