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. Author manuscript; available in PMC: 2018 May 1.
Published in final edited form as: Cancer Epidemiol Biomarkers Prev. 2016 Dec 8;26(5):692–701. doi: 10.1158/1055-9965.EPI-16-0721

Table 3.

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

Risk Factors Non-Hispanic White US Hispanic Pinteraction
0–43% Native American Ancestry 43.1%–100% Native American Ancestry



Cases (n = 875) Controls (n=979) OR (95% CI)a Cases (n =332) Controls (n = 369) OR (95% CI)a Cases (n = 282) Controls (n = 416) OR (95% CI)a
Ageb, y 0.98 (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
 Yes 201 (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)
 No 674 (77.0) 817 (83.4) Referent 256 (77.1) 316 (85.6) Referent 237 (84.0) 367 (88.2) Referent
No. births and age at first birthc, No. (%) 0.76
 Nulliparous 126 (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 y 186 (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 y 172 (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 y 305 (34.9) 378 (38.6) Referent 143 (43.1) 184 (49.9) Referent 143 (50.7) 237 (57.0) Referent
 ≥3, ≥25 y 86 (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
 None 416 (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)
 ≤12 272 (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)
 >12 187 (21.4) 214 (21.9) Referent 77 (23.2) 103 (27.9) Referent 74 (26.2) 146 (35.1) Referent
Ptrend = 0.31 Ptrend = 0.06 Ptrend = 0.09
Body mass indexb, kg/m2, No. (%) 0.76
 <25.0 347 (39.7) 397 (40.6) Referent 96 (28.9) 85 (23.0) Referent 48 (17.0) 63 (15.1) Referent
 25.0–29.9 279 (31.9) 304 (31.1) 1.09 (0.87, 1.37) 110 126 (34.2) 0.76 (0.51, 1.14) 102 (36.2) 151 (36.3) 1.08 (0.66, 1.75)
 ≥30 249 (28.4) 278 (28.4) 1.03 (0.81, 1.30) (33.1) 158 (42.8) 0.65 (0.44, 0.98) 132 (46.8) 202 (48.6) 1.07 (0.67, 1.71)
Ptrend = 0.78 126 (38.0) Ptrend = 0.04 Ptrend = 0.82
Age at menarche, y, No. (%) 0.80
 ≤11 197 (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)
 12–13 469 (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)
 ≥14 209 (23.9) 271 (27.7) Referent 91 (27.4) 113 (30.6) Referent 90 (31.9) 129 (31.0) Referent
Ptrend = 0.02 Ptrend = 0.11 Ptrend = 0.99
Age at menopause, y, No. (%) 0.30
 ≤50 493 (56.3) 593 (61.1) Referent 205 (61.8) 232 (62.9) Referent 176 (62.4) 294 (70.7) Referent
 >50 382 (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
 Current 469 (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)
 Former 189 (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)
 Never 217 (24.8) 231 (23.6) Referent 123 (37.0) 146 (39.5) Referent 127 (45.0) 186 (44.7) Referent
Ptrend = 0.39 Ptrend = 0.04 Ptrend = 0.06
Alcohol consumptione, g/day, No. (%) 0.58
 None 413 (47.2) 510 (52.1) Referent 219 (66.0) 235 (63.7) Referent 201 (71.3) 316 (76.0) Referent
 <10 328 (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)
 ≥10 134 (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 = 0.06 Ptrend = 0.49 Ptrend = 0.89

OR, odds ratio; CI, confidence interval. Results in bold are statistically significant, results in italics are marginally significant.

a

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

b

In referent year.

c

Includes live or still birth

d

Includes both parous and non-parous women.

e

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