Table 1.
Main characteristics of cases and controls from the study population
| Variable | Category | Cases | Controls | p |
|---|---|---|---|---|
| Age, mean ± sd | 56.4 ± 12.6 | 59.0 ± 13.2 | <0.001 | |
| Geographical area, n (%) | Asturias | 70 (4.0) | 121 (6.4) | |
| Barcelona | 292 (16.8) | 380 (20.1) | ||
| Cantabria | 141 (8.1) | 188 (9.9) | ||
| Gerona | 47 (2.7) | 57 (3.0) | ||
| Guipuzcoa | 226 (13.0) | 255 (13.5) | ||
| Huelva | 105 (6.1) | 79 (4.2) | ||
| Leon | 227 (13.1) | 202 (10.7) | ||
| Madrid | 341 (19.6) | 365 (19.3) | ||
| Navarra | 226 (13.0) | 181 (9.6) | ||
| Valencia | 61 (3.5) | 67 (3.5) | <0.001 | |
| Family history of breast cancer, n (%) | No | 1288 (75.0) | 1628 (85.7) | |
| First-degree relative | 256 (14.9) | 166 (8.7) | ||
| Second-degree relative | 174 (10.1) | 106 (5.8) | <0.001 | |
| Educational level, n (%) | Less than primary school | 268 (15.4) | 327 (17.3) | |
| Primary school | 565 (32.6) | 581 (30.7) | ||
| Secondary school | 573 (33.0) | 585 (30.9) | ||
| University | 330 (19.0) | 402 (21.2) | 0.10 | |
| Tobacco smoking, n (%) | Never smoker | 972 (56.0) | 1141 (60.2) | |
| Former smoker | 450 (25.9) | 397 (21.0) | ||
| Current smoker | 314 (18.1) | 357 (18.8) | 0.002 | |
| Body Mass Index (kg/m2), n (%) | <18.5 | 30 (1.7) | 43 (2.3) | |
| 18.5–24.9 | 789 (45.5) | 899 (47.4) | ||
| 25.0–29.9 | 590 (34.0) | 601 (31.7) | ||
| ≥30 | 327 (18.8) | 352 (18.6) | 0.31 | |
| Energy intake (kcal/day), mean ± sd | 1861 ± 644 | 1754 ± 566 | <0.001 | |
| Ethanol intake (g/day), mean ± sd | 6.2 ± 11.5 | 5.3 ± 9.5 | 0.01 | |
| Red meat intake (g/day), mean ± sd | 26.9 ± 20.2 | 25.2 ± 19.9 | 0.01 | |
| Fruit intake (g/day), mean ± sd | 363 ± 239 | 365 ± 222 | 0.87 | |
| Vegetable intake (g/day), mean ± sd | 196 ± 133 | 198 ± 119 | 0.60 | |
| Dairy intake (g/day), mean ± sd | 321.1 ± 177.1 | 328.7 ± 176.7 | 0.24 | |
| Number of deliveries, mean ± sd | 1.9 ± 1.5 | 2.0 ± 1.6 | 0.03 | |
| Menopausal status, n (%) | Premenopausal | 702 (40.4) | 628 (33.1) | |
| Postmenopausal | 1034 (59.6) | 1267 (66.9) | <0.001 | |
| Age at first delivery, mean ± sd | 26.5 ± 5.0 | 26.5 ± 4.7 | 0.82 | |
| Age at menarche, mean ± sd | 12.8 ± 1.5 | 12.9 ± 1.5 | 0.02 | |
| Age at menopause, mean ± sd | 48.8 ± 5.4 | 48.5 ± 5.3 | 0.18 | |
| Previous use of hormonal contraceptives, n (%) | 789 (45.5) | 868 (45.8) | 0.83 |