Table 1 Participant characteristics at blood collection
Characteristic | Cases (n= 98) | Controls (n= 168) | Â |
|---|---|---|---|
Continuous variables | Mean ± SD | P a | |
   Age, years | 44.7 ± 4.8 | 44.6 ± 4.5 | 0.10 |
   Height, cm | 163.4 ± 6.0 | 163.5 ± 5.8 | 0.95 |
   BMI, kg/m2 | 25.7 ± 5.1 | 25.2 ± 4.8 | 0.35 |
   Menarche, years | 12.5 ± 1.3 | 12.8 ± 1.4 | 0.08 |
   Age at first pregnancy, yearsb | 22.2 ± 4.3 | 22.1 ± 4.1 | 0.92 |
   Number of term pregnancies | 2.7 ± 1.6 | 2.9 ± 1.7 | 0.50 |
Categoric variables | Frequency, number (%) | P a | |
   Nulliparous | 9 (9.2%) | 13 (7.7%) | 0.82 |
   Smoking status |  |  | 0.50 |
   Never | 61 (62.2%) | 103 (61.3%) |  |
   Former | 19 (19.4%) | 26 (15.5%) |  |
   Current | 18 (18.4%) | 39 (23.2%) |  |
   History of breast cancer in first-degree relative | 17 (17.4%) | 14 (8.3%) | 0.03 |
   Menstrual cycle day at blood collection |  |  | 0.45 |
Days 0-13 | 35 (35.7%) | 68 (40.5%) | Â |
Days 14-33 | 40 (40.8%) | 68 (40.5%) | Â |
Days ≥34 | 9 (9.2%) | 13 (7.7%) |  |
Unknown | 14 (14.3%) | 19 (11.3%) | Â |