Table 2.

Selected reproductive characteristics of breast cancer cases and control women, Shanghai, China

CharacteristicCases, n = 378 (age-adjusted %)*Controls, n = 1,070 (%)
Age at menarche
    ≤1366 (19.9)171 (15.6)
    1469 (19.9)204 (19.1)
    1591 (23.2)215 (20.1)
    1668 (16.8)221 (20.7)
    ≥1784 (20.1)257 (24.0)
No. live births
    021 (5.4)41 (3.8)
    1193 (63.6)713 (66.6)
    266 (13.4)124 (11.6)
    >397 (17.4)188 (17.6)
    Missing1 (0.2)4 (0.4)
Age at 1st live birth (y)
    No live birth21 (5.4)41 (3.8)
    ≤24118 (21.9)275 (25.7)
    25-29170 (52.4)599 (56.0)
    ≥3065 (19.5)151 (14.1)
    Missing4 (0.8)4 (0.4)
Duration of breast-feeding(mos)
    Never73 (21.5)233 (21.8)
    ≤669 (20.0)209 (19.5)
    7-12104 (32.5)361 (33.7)
    13-2455 (11.6)115 (10.8)
    ≥2577 (13.9)152 (14.2)
Duration of oral contraceptive use (y)
    Never used332 (89.0)978 (91.4)
    ≤121 (5.8)35 (3.3)
    ≥125 (5.3)56 (5.2)
Induced abortions
    0163 (40.7)437 (40.8)
    1138 (37.1)427 (39.9)
    ≥256 (16.8)167 (15.6)
    Missing21 (5.4)39 (3.7)
Years since last induced abortion
    None163 (40.7)437 (40.8)
    0-1041 (14.6)129 (12.1)
    11-1549 (16.7)185 (17.3)
    16-2029 (7.6)120 (11.2)
    >2054 (10.1)145 (13.6)
    Missing years42 (10.3)54 (5.1)
No. prior benign breast lumps
    0360 (94.5)1,038 (97.0)
    113 (3.9)22 (2.1)
    ≥25 (1.6)10 (0.9)
Times breast self-examination/y
    0198 (50.8)725 (67.8)
    1-680 (21.4)137 (12.8)
    7-1285 (23.8)198 (18.5)
    ≥1310 (3.1)7 (0.7)
    Missing5 (0.9)3 (0.2)
Menopause
    No187 (62.7)687 (64.2)
    Yes191 (37.3)383 (35.8)
  • NOTE: P value for age-adjusted model stratified by year of interview (1995-1996, 1997, 1998-1999, and 2000-2001), using conditional logistic regression.

  • * Indirect age-adjusted percentages based on age distribution of the controls.

  • P < 0.01.

  • P < 0.01.