TABLE 1.
Main characteristics of the study population.
| Controls (N = 1,326) mean (SD) or N (%) |
Cases (N = 1,181) mean (SD) or N (%) |
|
| Age (years) | 58.4 (12.5) | 55.4 (11.6) |
| BMI (kg/m2) | 25.7 (4.7) | 25.9 (0.187) |
| Education | ||
| Less than primary school | 193 (14.6) | 137 (11.6) |
| Primary school | 412 (31.1) | 403 (34.1) |
| Secondary school | 438 (33.0) | 407 (34.5) |
| University | 283 (21.3) | 234 (19.8) |
| Score socioeconomic | ||
| Low | 357 (27.8) | 334 (28.3) |
| Medium | 696 (54.2) | 660 (55.9) |
| High | 232 (18.1) | 187 (15.8) |
| Family history of breast cancer | ||
| Yes | 124 (9.4) | 175 (14.8) |
| No | 1,202 (90.6) | 1,006 (85.2) |
| Diabetes | ||
| No | 1,222 (92.4) | 1,104 (93.9) |
| Yes | 100 (7.6) | 72 (6.1) |
| Age at menarche (years) | 12.8 (1.6) | 12.7 (1.5) |
| Number of children | ||
| Nulliparous | 236 (17.8) | 243 (20.6) |
| 1–2 children | 745 (56.3) | 694 (58.8) |
| 3 children or more | 342 (25.9) | 243 (20.6) |
| Age at first child | ||
| First child < 20 years old | 52 (4.8) | 46 (4.9) |
| First child 20–35 years old | 957 (88.1) | 811 (86.9) |
| Parous ≥ 35 years old | 77 (7.1) | 76 (8.1) |
| Breastfeeding | ||
| Parous without breastfeeding | 166 (15.3) | 141 (15.5) |
| Parous breastfeeding for less than 6 months | 294 (27.2) | 269 (29.6) |
| Parous breastfeeding for 6–24 months | 496 (45.8) | 423 (46.5) |
| Parous breastfeeding for more than 24 months | 126 (11.6) | 76 (8.4) |
| Contraceptive use | ||
| Never | 648 (48.9) | 603 (51.1) |
| Ever | 677 (51.1) | 577 (48.9) |
| Menopausal status | ||
| Premenopausal | 386 (29.1) | 436 (36.9) |
| Postmenopausal | 940 (70.9) | 745 (63.1) |
| Hormonal replacement therapy | ||
| Never | 1,178 (92.0) | 1,071 (92.5) |
| Ever | 102 (8.0) | 87 (7.5) |
| Smoking | ||
| Never smoker | 778 (58.7) | 662 (56.1) |
| Past smoker | 292 (22.0) | 311 (26.4) |
| Current smoker | 256 (19.3) | 207 (17.5) |
| Daily alcohol intake (g ethanol) | 6.0 (10.1) | 6.9 (12.7) |
| Daily caloric intake (Kcal) | 1,717.8 (537.4) | 1,831.6 (610.5) |
| Daily consumption of vegetables and fruits (g) | 557.0 (264.4) | 555.8 (300.2) |
| Physical activitya | ||
| Inactive | 516 (38.9) | 500 (42.3) |
| Poorly active | 255 (19.2) | 203 (17.2) |
| Moderately active | 167 (12.6) | 147 (12.4) |
| Very active | 387 (29.2) | 331 (28.0) |
| Chronotype | ||
| Morning | 508 (38.8) | 426 (36.5) |
| Intermediate | 528 (40.3) | 464 (39.7) |
| Evening | 273 (20.9) | 278 (23.8) |
| Sleep duration (hours) | 6.9 (1.3) | 7.1 (1.3) |
| Breakfast | ||
| Never | 9 (0.7) | 21 (1.8) |
| Only weekends | 10 (0.8) | 6 (0.5) |
| Only weekdays | 20 (1.5) | 24 (2.0) |
| Always | 1,279 (97.0) | 1,129 (95.7) |
| Time of breakfast (start time, a.m.) | 8.4 (1.4) | 8.5 (1.4) |
| Nighttime fasting duration (hours) | 11.0 (1.6) | 11.1 (1.6) |
BMI, body mass index; N, sample size; SD, standard deviation.
aPhysical activity was classified according to the annual mean of METS h/week. Inactive = 0 METS h/week; poorly active = 0.0001–8 METS h/week; moderately active = 8.0001–16 METS h/week; very active = more than 16.0001 METS h/week.