Table 1.

Characteristics of study participants: comparison of cases and controls for all study participants and for subset whose mothers were interviewed and comparison of study participants by whether mother was interviewed

All study participants
Subset with data from mothers
All study participants
No. (%) cases (n = 597)No. (%) controls (n = 966)No. (%) cases (n = 99)No. (%) controls (n = 156)No. (%) mothers interviewed (n = 255)No. (%) mothers not interviewed (n = 1,308)
Age at diagnosis*
    20-39137 (23)270 (28)35 (36)75 (48)110 (43)297 (23)
    40-44108 (18)191 (20)32 (32)36 (23)68 (27)231 (18)
    45-49154 (26)190 (20)19 (19)29 (19)48 (19)296 (23)
    ≥50198 (33)315 (33)13 (13)16 (10)29 (11)484 (37)
P = 0.05P = 0.15P < 0.0001
Race
    Chinese164 (27)288 (30)26 (26)51 (33)77 (30)375 (29)
    Japanese239 (40)395 (41)53 (54)82 (52)135 (53)499 (38)
    Filipino194 (33)283 (29)20 (20)23 (15)43 (17)434 (33)
P = 0.17P = 0.17P = 0.0007
Study center
    Hawaii213 (36)379 (39)38 (39)84 (54)122 (48)470 (36)
    Los Angeles215 (36)274 (28)28 (28)23 (15)51 (20)438 (34)
    San Francisco-Oakland169 (28)313 (32)33 (33)49 (31)82 (32)400 (31)
P = 0.90P = 0.12P = 0.07
Parity
    Nulliparous145 (25)148 (15)38 (38)24 (15)62 (24)231 (18)
    1 live birth85 (14)141 (15)19 (19)34 (22)53 (21)173 (13)
    2-3 live births288 (49)481 (50)37 (38)76 (49)113 (44)656 (51)
    ≥4 live births73 (12)188 (20)5 (5)22 (14)27 (11)234 (18)
P < 0.0001P < 0.0001P = 0.31
Age at first live birth
    Nulliparous145 (25)148 (15)38 (38)24 (15)62 (24)231 (18)
    ≤2030 (5)96 (10)2 (2)18 (12)20 (8)106 (8)
    21-30314 (53)583 (61)39 (40)92 (59)131 (51)766 (59)
    ≥31101 (17)128 (13)20 (20)22 (14)42 (17)187 (15)
P = 0.06P = 0.02P = 0.67
Menopausal status at diagnosis
    Premenopausal438 (74)684 (71)88 (89)136 (87)224 (88)898 (69)
    Postmenopausal151 (26)277 (29)11 (11)20 (13)31 (12)397 (31)
P = 0.17P = 0.68P = 0.92
Age at menarche
    ≤11105 (18)160 (17)19 (19)48 (31)67 (26)198 (15)
    12-13284 (48)457 (48)60 (61)82 (53)142 (56)599 (46)
    14-15138 (23)225 (23)16 (16)21 (13)37 (15)326 (25)
    ≥1663 (11)117 (12)4 (4)4 (3)8 (3)172 (13)
P = 0.36P = 0.07P = 0.004
Family history of breast cancer
    First- or second-degree relative117 (20)92 (10)18 (18)22 (14)40 (16)169 (13)
    No relatives480 (80)874 (90)81 (82)134 (86)215 (84)1139 (87)
P < 0.0001P = 0.38P = 0.67
Personal history of benign breast disease
    Yes104 (18)98 (10)23 (23)22 (14)45 (18)162 (13)
    No469 (82)840 (90)76 (77)134 (86)210 (82)1134 (87)
P < 0.0001P = 0.06P = 0.05
  • * An age comparable with the age at diagnosis of breast cancer was assigned to each of the controls based on the ages at diagnosis of the frequency-matched cases (2).

  • P values are adjusted for subject's age and place of birth, as these variables reflect the basis for identifying the mothers eligible for interview.