Table 1.
Participant baseline characteristics among breast cancer cases and controls.
| Characteristics | Cases (n = 973) | Controls (n = 973) | p value | ||
|---|---|---|---|---|---|
| Age, mean (±SD) | 50.4 | (±9.6) | 50.2 | (±9.4) | 0.562a |
| Educational level, n(%) | |||||
| No formal education - First grade | 208 | (22) | 160 | (16) | |
| Second grade - Vocational training | 510 | (52) | 491 | (51) | |
| University graduate | 255 | (26) | 322 | (33) | 0.001a |
| Age at menarche, mean(±SD) | 12.6 | (±1.5) | 12.4 | (±1.5) | 0.049b |
| Age at first birth, mean(±SD) | 26.5 | (±4.3) | 26.2 | (±4.3) | 0.097b |
| Number of children, n(%) | |||||
| None | 215 | (22) | 220 | (23) | |
| 1–2 | 593 | (61) | 587 | (60) | |
| 3–4 | 151 | (16) | 149 | (15) | |
| >4 | 14 | (1) | 17 | (2) | 0.942a |
| Menopausal status, n(%) | |||||
| Premenopausal | 551 | (57) | 513 | (53) | |
| Posmenopausal | 422 | (43) | 460 | (47) | 0.084a |
| Body mass index, Kg/m2, mean(±SD) | |||||
| Premenopausal | 24.4 | (±5.9) | 24.7 | (±5.9) | 0.225b |
| Posmenopausal | 27.3 | (±8.1) | 26.2 | (±6.4) | 0.004b |
| Hormone replacement therapy use, n(%) | |||||
| Never | 864 | (89) | 874 | (90) | |
| Ever | 109 | (11) | 99 | (10) | 0.432b |
| Previous benign breast problems, n(%) | |||||
| No | 761 | (78) | 796 | (82) | |
| Yes | 212 | (22) | 177 | (18) | 0.047a |
| Family history of breast cancer, n(%) | |||||
| None | 728 | (75) | 782 | (80) | |
| Second degree | 129 | (13) | 105 | (11) | |
| First degree | 116 | (12) | 86 | (9) | 0.012a |
| Self-assessed physical activity last year, n(%) | |||||
| Sedentary/slightly active | 365 | (37) | 312 | (32) | |
| Moderately active | 339 | (35) | 394 | (41) | |
| Active/very active | 269 | (28) | 267 | (27) | 0.126b |
| Smoking status, n(%) | |||||
| Never smoker | 420 | (43) | 404 | (42) | |
| Former smoker for ≥6 mo. | 258 | (27) | 254 | (26) | |
| Smoker or former smoker for <6 mo. | 295 | (30) | 315 | (32) | 0.287b |
| Caloric intake (Kcal/day), mean(±SD) | 1990.2 | (±615.1) | 1897.2 | (±628.4) | 0.001a |
| Basal metabolic rate (Kcal/day), mean(±SD) | 1316.2 | (±137.6) | 1309.8 | (±122.8) | 0.263b |
| Predicted calories (Kcal/day), mean(±SD) | 1694.5 | (±305.2) | 1718.8 | (±291.1) | 0.072a |
| Mediterranean dietary pattern scorec, n(%) | |||||
| <5.0812 | 254 | (26) | 243 | (25) | |
| 5.0812–6.0047 | 250 | (26) | 243 | (25) | |
| 6.0048–6.8686 | 263 | (27) | 244 | (25) | |
| >6.8686 | 206 | (21) | 243 | (25) | 0.250a |
| Western dietary pattern scorec, n(%) | |||||
| <4.104 | 208 | (22) | 243 | (25) | |
| 4.104–5.150 | 216 | (22) | 243 | (25) | |
| 5.151–6.197 | 254 | (26) | 244 | (25) | |
| >6.197 | 295 | (30) | 243 | (25) | 0.023a |
| Tumour subtyped, n(%) | |||||
| HR+ | 653 | (67) | |||
| HER2+ | 199 | (21) | |||
| TN | 119 | (12) | |||
Abbreviations: SD = standard deviation; HR+= hormone receptor positive tumours (ER+ and/or PR + , with HER2−); HER2+= human epidermal growth factor receptor 2 positive tumours; TN = triple negative tumours.
ap value resulting from Pearson Chi-Square test (variables with no missing values).
bp value resulting from conditional logistic regression models (variables with imputed values).
cAccording to the quartiles in the control group.
dTwo breast cancer cases could not be classified.