Table 1.

Baseline characteristics of postmenopausal breast cancer cases and controls

Cases (ntotal = 324)*, n (%)Controls (ntotal = 651)*, n (%)P
Age (y)0.96
    ≤5533 (10.2)70 (10.8)
    55-<65135 (41.7)269 (41.3)
    ≥65156 (48.2)312 (47.9)
Race: Caucasian308 (95.1)619 (95.1)0.99
Education: some college or more239 (74.9)476 (74.1)0.79
Married/living with partner221 (69.1)455 (71.2)0.49
Body mass index (kg/m2)0.27
    <25.0140 (45.3)245 (39.9)
    25.0-<30.0102 (33.0)216 (35.2)
    30.0 or ≥3067 (21.7)153 (24.9)
Smoking0.54
    Never162 (50.3)348 (53.9)
    Former141 (43.8)259 (40.1)
    Current19 (5.9)39 (6.0)
Family history of breast cancer0.36
    None256 (81.0)539 (84.2)
    1 first-degree relative with breast cancer52 (16.5)91 (14.2)
    2+ first-degree relatives with breast cancer8 (2.5)10 (1.6)
Mammogram within last 2 y300 (93.2)609 (93.8)0.69
Prior breast biopsy90 (28.0)141 (21.7)0.03
Surgical menopause53 (16.4)113 (17.4)0.70
Ever used oral contraceptives215 (67.2)419 (64.7)0.44
Age at menarche (y)0.67
    ≤1165 (20.1)119 (18.4)
    1291 (28.2)176 (27.2)
    13101 (31.3)197 (30.5)
    ≥1466 (20.4)154 (23.8)
Age at first birth (y)0.05
    ≤1946 (14.2)103 (9.9)
    20-24129 (39.8)295 (45.8)
    25-2973 (22.5)142 (22.1)
    ≥3035 (10.8)40 (6.2)
    No births41 (12.7)64 (9.9)
Parity0.01
    Nulliparous41 (13.4)64 (10.8)
    135 (11.4)60 (10.2)
    2108 (35.3)177 (30.0)
    373 (23.9)131 (22.2)
    4+49 (16.0)159 (26.9)
Age at menopause (y)0.34
    ≤4466 (21.8)154 (26.1)
    45-4994 (31.0)167 (28.3)
    ≥50143 (47.2)269 (45.6)
  • * The numbers do not always add up to the total number of cases and controls due to missing information.

  • χ2 test.