Table 3.

Relationship between risk factors and breast cancer risk among postmenopausal non-Hispanic Whites and US Hispanics according to percent NA ancestry

US Hispanic
Non-Hispanic White0–43% NA Ancestry43.1%–100% NA Ancestry
Risk FactorsCases (n = 875)Controls (n = 979)OR (95% CI)aCases (n = 332)Controls (n = 369)OR (95% CI)aCases (n = 282)Controls (n = 416)OR (95% CI)aPinteraction
Ageb, y0.98 (0.97–0.99)1.01 (0.99–1.02)1.00 (0.98–1.02)0.20
Family history of breast cancer, No. (%)0.93
 Yes201 (23.0)162 (16.6)1.57 (1.24–1.99)76 (22.9)53 (14.4)1.82 (1.22–2.73)45 (16.0)49 (11.8)1.61 (1.01–2.55)
 No674 (77.0)817 (83.4)Referent256 (77.1)316 (85.6)Referent237 (84.0)367 (88.2)Referent
No. births and age at first birthc, No. (%)0.76
 Nulliparous126 (14.4)125 (12.8)1.00 (0.72–1.40)25 (7.5)28 (7.6)0.89 (0.47–1.68)30 (10.6)20 (4.8)2.10 (1.07–4.12)
 1–2, <25 y186 (21.3)192 (19.6)1.13 (0.68–1.48)62 (18.7)56 (15.2)1.30 (0.82–2.07)48 (17.0)49 (11.8)1.60 (0.98–2.62)
 1–2, ≥25 y172 (19.7)171 (17.5)1.14 (0.87–1.50)61 (18.4)58 (15.7)1.24 (0.79–1.95)36 (12.8)47 (11.3)1.15 (0.69–1.93)
 ≥3, <25 y305 (34.9)378 (38.6)Referent143 (43.1)184 (49.9)Referent143 (50.7)237 (57.0)Referent
 ≥3, ≥25 y86 (9.8)113 (11.5)0.99 (0.71–1.37)41 (12.4)43 (11.7)1.14 (0.69–1.89)25 (8.9)63 (15.1)0.67 (0.40–1.14)
Breastfeedingd, mos, No. (%)0.31
 None416 (47.5)409 (41.8)1.11 (0.84–1.46)159 (47.9)147 (39.8)1.42 (0.95–2.12)135 (47.9)146 (35.1)1.43 (0.94–2.17)
 ≤12272 (31.1)356 (36.1)0.86 (0.66–1.12)96 (28.9)117 (32.3)0.95 (0.62–1.46)73 (25.9)124 (29.8)1.03 (0.67–1.58)
 >12187 (21.4)214 (21.9)Referent77 (23.2)103 (27.9)Referent74 (26.2)146 (35.1)Referent
Ptrend = 0.31Ptrend = 0.06Ptrend = 0.09
Body mass indexb, kg/m2, No. (%)0.76
 <25.0347 (39.7)397 (40.6)Referent96 (28.9)85 (23.0)Referent48 (17.0)63 (15.1)Referent
 25.0–29.9279 (31.9)304 (31.1)1.09 (0.87–1.37)110 (33.1)126 (34.2)0.76 (0.51–1.14)102 (36.2)151 (36.3)1.08 (0.66–1.75)
 ≥30249 (28.4)278 (28.4)1.03 (0.81–1.30)126 (38.0)158 (42.8)0.65 (0.44–0.98)132 (46.8)202 (48.6)1.07 (0.67–1.71)
Ptrend = 0.78Ptrend = 0.04Ptrend = 0.82
Age at menarche, y, No. (%)0.80
 ≤11197 (22.5)183 (18.7)1.38 (1.05–1.82)93 (28.0)81 (22.0)1.44 (0.93–2.21)66 (23.4)84 (20.2)1.04 (0.66–1.63)
 12–13469 (53.6)525 (53.6)1.13 (0.90–1.41)148 (44.6)175 (47.4)1.08 (0.75–1.56)126 (44.7)203 (48.8)0.81 (0.55–1.17)
 ≥14209 (23.9)271 (27.7)Referent91 (27.4)113 (30.6)Referent90 (31.9)129 (31.0)Referent
Ptrend = 0.02Ptrend = 0.11Ptrend = 0.99
Age at menopause, y, No. (%)0.30
 ≤50493 (56.3)593 (61.1)Referent205 (61.8)232 (62.9)Referent176 (62.4)294 (70.7)Referent
 >50382 (43.7)377 (38.9)1.35 (1.11–1.65)129 (38.2)137 (37.1)1.05 (0.75–1.46)106 (37.6)122 (29.3)1.60 (1.13–2.28)
Hormone therapy useb, No. (%)0.07
 Current469 (53.6)478 (48.8)1.04 (0.83–1.31)139 (41.9)111 (30.1)1.49 (1.03–2.15)104 (36.9)96 (23.1)1.63 (1.11–2.41)
 Former189 (21.6)270 (27.6)0.75 (0.57–0.98)70 (21.1)112 (30.4)0.72 (0.48–1.09)51 (18.1)134 (32.2)0.52 (0.35–0.79)
 Never217 (24.8)231 (23.6)Referent123 (37.0)146 (39.5)Referent127 (45.0)186 (44.7)Referent
Ptrend = 0.39Ptrend = 0.04Ptrend = 0.06
Alcohol consumptione, g/day, No. (%)0.58
 None413 (47.2)510 (52.1)Referent219 (66.0)235 (63.7)Referent201 (71.3)316 (76.0)Referent
 <10328 (37.5)336 (34.3)1.19 (0.94–1.47)85 (25.6)106 (28.7)0.79 (0.55–1.14)66 (23.4)79 (19.0)1.10 (0.73–1.65)
 ≥10134 (15.3)133 (13.6)1.26 (0.94–1.67)27 (8.4)28 (7.6)0.99 (0.56–1.77)15 (5.3)21 (5.0)0.92 (0.45–1.90)
Ptrend = 0.06Ptrend = 0.49Ptrend = 0.89
  • NOTE: Results in bold are statistically significant, results in italics are marginally significant.

    Abbreviations: CI, confidence interval; OR, odds ratio.

  • aAdjusted for study site (San Francisco Bay Area Breast Cancer Study versus 4-Corners) and all the listed factors.

  • bIn referent year.

  • cIncludes live or still birth.

  • 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).