Characteristics of study controls by plasma ferritin quartile in the NHSII [mean (SD) or %]
| Ferritin quartile, ng/mL | |||||
|---|---|---|---|---|---|
| Range: | ≤23.9 | >23.9–≤42.1 | >42.1–≤72.0 | >72.0 | |
| Characteristic | Median | 15.0 | 32.2 | 55.0 | 107 |
| Number | 198 | 199 | 199 | 199 | |
| Age at blood draw, years | 44.2 (4.1) | 44.2 (4.4) | 45.0 (4.5) | 46.2 (4.4) | |
| Age at menarche, years | 12.6 (1.4) | 12.5 (1.5) | 12.5 (1.4) | 12.4 (1.5) | |
| BMI at age 18, kg/m2 | 20.7 (2.7) | 21.0 (3.2) | 21.0 (2.8) | 21.5 (3.2) | |
| BMI at blood draw, kg/m2 | 24.8 (5.4) | 25.3 (5.3) | 25.4 (5.2) | 28.2 (6.8) | |
| Weight change since age 18, kg | 10.9 (11.7) | 11.7 (11.1) | 12.0 (12.0) | 18.0 (15.4) | |
| Nulliparous | 16.2% | 20.6% | 18.6% | 19.6% | |
| Parity, childrena | 2.5 (1.0) | 2.4 (0.9) | 2.3 (1.0) | 2.2 (1.0) | |
| Age at first birth, yearsa | 25.9 (3.9) | 26.3 (4.5) | 26.8 (4.9) | 26.2 (5.1) | |
| Ever breast feda | 80.7% | 81.7% | 80.9% | 75.6% | |
| Ever use of oral contraceptives | 83.3% | 84.4% | 91.0% | 90.0% | |
| Duration of oral contraceptive use, monthsb | 51.2 (41.7) | 53.5 (45.3) | 50.6 (47.8) | 54.3 (44.4) | |
| Family history of breast cancer | 13.1% | 11.6% | 4.5% | 11.1% | |
| History of biopsy-confirmed benign breast disease | 16.2% | 17.6% | 16.1% | 11.1% | |
| Premenopausal at blood draw | 91.4% | 83.9% | 73.4% | 53.8% | |
| Use of iron supplements at blood draw | 6.7% | 4.6% | 7.1% | 10.0% | |
| Total red meat intake, servings/weekc | 4.9 (3.1) | 5.1 (3.2) | 5.0 (3.1) | 5.7 (3.6) | |
| Processed red meat intake, servings/weekc | 1.3 (1.3) | 1.3 (1.5) | 1.2 (1.3) | 1.5 (1.7) | |
| Unprocessed red meat intake, servings/weekc | 3.6 (2.3) | 3.8 (2.5) | 3.8 (2.4) | 4.2 (2.4) | |
| Saturated fat intake, g/dayc | 21.1 (7.1) | 21.8 (7.7) | 20.7 (7.1) | 21.9 (8.4) | |
| Energy intake, kcal/dayc | 1,790 (456) | 1,867 (504) | 1,776 (478) | 1,806 (523) | |