Table 1.
Characteristics of breast cancer cases and controls in the NHS IIa
| Cases (n = 584) | Controls (n = 584) | |
|---|---|---|
| Age at blood collection (year) | 45.1 (4.5) | 45.0 (4.4) |
| Age at menarche, ≥13 years (%) | 45 | 46 |
| BMI at age 18 (kg/m2) | 20.7 (2.7) | 21.1 (3.0) |
| BMI at blood collection (kg/m2) | 25.0 (5.0) | 26.0 (6.1) |
| Smoking, current (%) | 10 | 7 |
| Alcohol consumption, ≥1 drinks/week (%) | 39 | 34 |
| Physical activity, MET-h/week | 17.9 (25.0) | 18.9 (25.6) |
| Ever used oral contraceptive (%) | 85 | 88 |
| Duration of past oral contraceptive use, monthb | 55.4 (46.3) | 51.9 (44.2) |
| Nulliparous (%) | 22 | 20 |
| Parityc | 2.2 (0.9) | 2.4 (1.0) |
| Age at first birthc | 26.5 (4.6) | 26.0 (4.6) |
| Premenopausal at blood collection (%) | 76 | 74 |
| Family history of breast cancer (%) | 17 | 10 |
| History of benign breast disease (%) | 23 | 16 |
| Plasma 25(OH)Dd (nmol/L) | 62.6 (47.0, 78.1) | 61.4 (45.6, 76.4) |
| Calculated plasma-free 25(OH)Dd (pmol/L) | 19.5 (14.1, 26.3) | 19.2 (13.3, 25.5) |
| Plasma DBPd (nmol/L) | 4,642 (3,641, 5,671) | 4,626 (3,760, 5,588) |
a
Mean(standard deviation) for continuous variables and % for categorical variables
b
Duration of oral contraceptive use among ever users
c
Among parous women
d
Median (25, 75 %) values were given