Table 1.

Breast cancer risk factors among postmenopausal women according to region and self-reported ethnicity

US studies
Non-Hispanic WhiteHispanicMexico study
CharacteristicsCases (n = 875)Controls (n = 979)Cases (n = 614)Controls (n = 785)Cases (n = 426)Controls (n = 501)
US study site, No. (%)
 4-Corners740 (84.6)838 (85.6)309 (50.3)392 (49.9)N/AN/A
 San Francisco Bay Area135 (15.4)141 (14.4)305 (49.7)393 (50.1)
Reference agea,b, y, mean (SD)60.7 (9.2)62.0 (9.7)59.2 (9.1)59.2 (9.1)57.6 (7.4)56.3 (6.9)
Family historya,b, No. (%)
 Yes201 (23.0)162 (16.6)121 (19.7)102 (13.0)29 (6.8)12 (2.4)
 No674 (77.0)817 (83.4)493 (80.3)683 (87.0)397 (93.2)489 (97.6)
No. of birthsb,c, mean (SD)2.4 (1.6)2.6 (1.7)3.1 (2.1)3.7 (2.5)3.3 (2.4)4.3 (2.7)
Age at first birtha,b,c, y, mean (SD)23.5 (4.3)23.5 (4.5)23.0 (5.2)22.5 (4.9)23.0 (5.7)21.4 (4.9)
breastfeedingb,d, No. (%)
 Any459 (52.5)570 (58.2)320 (52.1)492 (62.7)326 (76.5)429 (85.6)
 None416 (47.5)409 (41.8)294 (47.9)293 (37.3)100 (23.5)72 (14.4)
Body mass index in referent yeara, kg/m2, mean (SD)27.6 (5.8)27.5 (6.0)29.6(6.1)30.2 (6.2)30.2(5.9)31.0 (5.6)
Age at menarche, y, mean (SD)12.6 (1.6)12.8 (1.6)12.6 (1.7)12.8 (1.8)12.8 (1.7)13.0 (1.6)
Age at menopauseb, y, mean (SD)46.2 (8.2)45.2 (8.2)45.7 (7.7)44.7 (7.6)45.7 (6.2)45.9 (6.4)
Hormone therapy usea,b, No. (%)
 Current469 (53.6)478 (48.8)243 (39.6)207 (26.4)18 (4.2)10 (2.0)
 Former189 (21.6)270 (27.6)121 (19.7)246 (31.3)84 (19.7)64 (12.8)
 Never217 (24.8)231 (23.6)250 (40.7)332 (42.3)324 (76.1)427 (85.2)
Alcohol consumptionb,e, No. (%)
 Any462 (52.8)469 (47.9)194 (31.6)234 (29.8)70 (16.4)33 (6.6)
 None413 (47.2)510 (52.1)420 (68.4)551 (70.2)356 (83.6)468 (93.4)
Percent NA ancestrya,b, mean (SD)0.04 (0.06)0.04 (0.04)0.41 (0.17)0.44 (0.18)0.66 (0.20)0.71 (0.19)
ER statusa
 ER+493 (82.9)348 (76.7)Not available
 ER102 (18.1)106(23.3)
  • aP < 0.05 when comparing NHW controls to US Hispanic controls or NHW cases to US Hispanic cases (ER status only).

  • bP < 0.05 when comparing US Hispanic controls to Mexico controls.

  • cAmong parous (live or still birth) women only (749 cases and 854 controls for NHW; US Hispanic= 559 cases and 737 controls for US Hispanic; 375 cases and 479 controls for Mexico).

  • dIncludes both parous and nonparous women.

  • eAlcohol consumption was based on lifetime average intake (4-Corners and Mexico subjects) or intake during the reference year (SFBCS).