Table 2.
Associations between risk factors and breast cancer subtypes in overall cases and controls.a
| Risk factors | Control, n (%) n = 1416 | Luminal n = 898 |
HER2-enriched n = 55 |
Triple-negative n = 303 |
Phd | |||
|---|---|---|---|---|---|---|---|---|
| n (%) | OR (95% CI) | n (%) | OR (95% CI) | n (%) | OR (95% CI) | |||
| Age, years | ||||||||
| <40 | 313 (22.1) | 221 (24.6) | 1.00 | 8 (14.5) | 1.00 | 48 (15.8) | 1.00 | |
| 40–59 | 896 (63.3) | 542 (60.4) | 0.72 (0.50–1.06) | 41 (74.5) | 0.53 (0.15–1.91) | 206 (68.0) | 0.67 (0.38–1.19) | 0.01 |
| ≥60 | 207 (14.6) | 135 (15.0) | 0.85 (0.67–1.07) | 6 (11.0) | 1.41 (0.62–3.24) | 49 (16.2) | 1.27 (0.86–1.87) | 0.15 |
| Ptrend = 0.42b | Ptrend = 0.64b | Ptrend = 0.04b | ||||||
| Menopausal status | ||||||||
| Yes | 585 (41.3) | 343 (38.2) | 1.00 | 25 (45.5) | 1.00 | 149 (49.2) | 1.00 | |
| No | 831 (58.7) | 555 (61.8) | 1.32 (1.05–1.65) | 30 (54.5) | 1.03 (0.54–1.96) | 154 (50.8) | 0.96 (0.71–1.33) | 0.02 |
| BMI, kg/m2 | ||||||||
| <18.5 | 82 (5.8) | 35 (3.9) | 1.00 | 2 (3.6) | 1.00 | 8 (2.6) | 1.00 | |
| 18.5–24.9 | 1149 (81.1) | 683 (76.1) | 1.58 (1.02–2.43) | 46 (83.6) | 1.41 (0.33–5.96) | 223 (73.6) | 1.77 (0.84–3.74) | 0.70 |
| ≥25 | 185 (13.1) | 180 (20.0) | 2.58 (1.60–4.14) | 7 (12.8) | 1.27 (0.25–6.36) | 72 (23.8) | 2.96 (1.34–6.54) | 0.39 |
| Ptrend < 0.001b | Ptrend = 0.76b | Ptrend < 0.001b | ||||||
| Age at menarche, years | ||||||||
| ≥15 | 925 (65.3) | 550 (61.2) | 1.00 | 44 (80.0) | 1.00 | 206 (68.0) | 1.00 | |
| 14 | 313 (22.1) | 213 (23.7) | 1.16 (0.94–1.43) | 6 (10.9) | 0.45 (0.19–1.08) | 59 (19.5) | 1.01 (0.73–1.41) | 0.03 |
| ≤13 | 178 (12.6) | 135 (15.1) | 1.28 (0.99–1.67) | 5 (9.1) | 0.75 (0.29–1.95) | 38 (12.5) | 1.22 (0.81–1.83) | 0.18 |
| Ptrend = 0.034b | Ptrend = 0.06b | Ptrend = 0.55b | ||||||
| Age at first live birth, yearsc | ||||||||
| ≤24 | 634 (46.0) | 370 (42.5) | 1.00 | 20 (36.4) | 1.00 | 134 (46.5) | 1.00 | |
| 25–29 | 682 (49.5) | 469 (53.9) | 1.41 (1.17–1.70) | 34 (61.8) | 2.08 (1.15–3.77) | 147 (51.0) | 1.34 (1.02–1.76) | 0.34 |
| ≥30 | 61 (4.6) | 31 (3.6) | 1.19 (0.75–1.90) | 1 (1.8) | 0.86 (0.11–6.72) | 7 (2.4) | 0.93 (0.41–2.13) | 0.56 |
| Ptrend = 0.28b | Ptrend = 0.37b | Ptrend = 0.50b | ||||||
| Breastfeedingc | ||||||||
| Yes | 1282 (93.1) | 821 (94.4) | 1.00 | 50 (90.9) | 1.00 | 267 (92.7) | 1.00 | |
| No | 95 (6.9) | 49 (5.6) | 0.92 (0.64–1.32) | 5 (9.1) | 1.57 (0.60–4.10) | 21 (7.3) | 1.24 (0.75–2.05) | 0.47 |
BMI, body mass index; CI, confidence interval; OR, odds ratio.
a
Odds ratios adjusted for the other factors in this table and family history of breast cancer.
b
P-value for trends calculated by trend chi-square.
c
Among parous women.
d
P-value of the heterogeneity of exposure-disease ORs between luminal, HER2-enriched, and triple-negative subtypes.