Table 2.
Selected characteristics of the study subjects and potential risk factors for breast cancer
| Cases (n = 547) (%) | Controls (n = 544) (%) | ORb (95% CI) | |
| Menopausal status | |||
| Premenopausal | 187 (34.2) | 230 (42.3) | 1.0 |
| Postmenopausal | 360 (65.8) | 314 (57.7) | 0.75 (0.44–1.29) |
| Age at menarche | |||
| <13 | 99 (18.1) | 87 (16.0) | 1.0 |
| 13–14 | 230 (42.0) | 212 (39.0) | 0.73 (0.54–1.06) |
| ≥ 15 | 218 (39.9) | 245 (45.0) | 0.91 (0.62–1.26) |
| Age at FFTP | |||
| Nulliparous | 116 (21.2) | 65 (11.9) | 1.0 |
| ≤ 25 | 269 (49.2) | 296 (54.4) | 0.76 (0.52–1.09) |
| 26–30 | 107 (19.6) | 138 (25.4) | 0.44 (0.30–0.65)** |
| ≥ 31 | 55 (10.0) | 45 (8.3) | 0.67 (0.38–1.12) |
| Number of full-term pregnancies | |||
| Nulliparous | 116 (21.2) | 65 (12.0) | 1.0 |
| 1 | 77 (14.1) | 72 (13.2) | 0.60 (0.37–0.95)** |
| 2 | 160 (29.2) | 204 (37.5) | 0.45 (0.32–0.63)* |
| 3+ | 194 (35.5) | 203 (37.3) | 0.55 (0.38–0.77)* |
| Use of oral contraceptives | |||
| Never | 359 (65.6) | 275 (50.6) | 1.0 |
| Ever | 188 (34.4) | 269 (49.4) | 0.55 (0.40–0.71)** |
| Postmenopausal use of estrogen | |||
| Never | 254 (70.6) | 208 (66.2) | 1.0 |
| Ever | 106 (29.4) | 106 (33.8) | 0.80 (0.60–1.02) |
| WHR | |||
| ≤ 0.91 | 216 (39.5) | 270 (49.6) | 1.0 |
| > 0.91 | 331 (60.5) | 274 (50.4) | 1.49 (1.17–1.91)** |
| BMI (kg/m2) | |||
| ≤ 25.4 | 243 (44.4) | 271 (49.8) | 1.0 |
| > 25.4 | 304 (55.6) | 273 (50.2) | 1.21 (0.96–1.55) |
| First-degree family history of breast cancer | |||
| No | 485 (88.7) | 519 (95.4) | 1.0 |
| Yes | 62 (11.3) | 25 (4.6) | 2.63 (1.60–4.40)** |
| History of benign breast disease | |||
| No | 340 (62.2) | 375 (68.9) | 1.0 |
| Yes | 207 (37.8) | 169 (31.1) | 1.32 (1.02–1.72)* |
| Educationa | |||
| Low | 332 (60.7) | 313 (57.5) | 1.0 |
| Medium | 144 (26.3) | 153 (28.1) | 0.87 (0.66–1.15) |
| High | 71 (13.0) | 78 (14.4) | 0.83 (0.57–1.25) |
| Current alcohol intake | |||
| Never | 309 (56.5) | 272 (50.0) | 1.0 |
| Once a month or less | 153 (28.0) | 172 (31.6) | 0.76 (0.57–1.03) |
| Daily-weekly | 85 (15.5) | 100 (18.4) | 0.74 (0.51–1.04) |
| Smoking habits | |||
| Nonsmokersc | 415 (75.9) | 396 (72.8) | 1.0 |
| Ex-smokersd | 59 (10.8) | 76 (14.0) | 0.72 (0.49–1.07) |
| Current smokerse | 73 (13.3) | 72 (13.2) | 0.95 (0.66–1.38) |
aLow: none or primary school; medium: middle school; high: high school, trade school or university. bAdjusted for age. OR: odds ratio; CI: confidencial intervals; FFTP: first full-term pregnancy; WHR: waist-hip ratio; BMI: body mass index. cNonsmokers = Never smokers; dEx-smokers = tobacco consumption stopped from 7.6 ± 4.2 years with a previous average tobacco consumption estimated at 47 pack-years (range, 20–106); e Current smokers = with an average tobacco consumption estimated at 43 pack-years (range, 20–200). *P < 0.05; **P < 0.01. The characteristics of participants with and without BC were compared by χ2 test for categorical variables.