Table 1.

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
CharacteristicMedian15.032.255.0107
Number198199199199
Age at blood draw, years44.2 (4.1)44.2 (4.4)45.0 (4.5)46.2 (4.4)
Age at menarche, years12.6 (1.4)12.5 (1.5)12.5 (1.4)12.4 (1.5)
BMI at age 18, kg/m220.7 (2.7)21.0 (3.2)21.0 (2.8)21.5 (3.2)
BMI at blood draw, kg/m224.8 (5.4)25.3 (5.3)25.4 (5.2)28.2 (6.8)
Weight change since age 18, kg10.9 (11.7)11.7 (11.1)12.0 (12.0)18.0 (15.4)
Nulliparous16.2%20.6%18.6%19.6%
Parity, childrena2.5 (1.0)2.4 (0.9)2.3 (1.0)2.2 (1.0)
Age at first birth, yearsa25.9 (3.9)26.3 (4.5)26.8 (4.9)26.2 (5.1)
Ever breast feda80.7%81.7%80.9%75.6%
Ever use of oral contraceptives83.3%84.4%91.0%90.0%
Duration of oral contraceptive use, monthsb51.2 (41.7)53.5 (45.3)50.6 (47.8)54.3 (44.4)
Family history of breast cancer13.1%11.6%4.5%11.1%
History of biopsy-confirmed benign breast disease16.2%17.6%16.1%11.1%
Premenopausal at blood draw91.4%83.9%73.4%53.8%
Use of iron supplements at blood draw6.7%4.6%7.1%10.0%
Total red meat intake, servings/weekc4.9 (3.1)5.1 (3.2)5.0 (3.1)5.7 (3.6)
Processed red meat intake, servings/weekc1.3 (1.3)1.3 (1.5)1.2 (1.3)1.5 (1.7)
Unprocessed red meat intake, servings/weekc3.6 (2.3)3.8 (2.5)3.8 (2.4)4.2 (2.4)
Saturated fat intake, g/dayc21.1 (7.1)21.8 (7.7)20.7 (7.1)21.9 (8.4)
Energy intake, kcal/dayc1,790 (456)1,867 (504)1,776 (478)1,806 (523)
  • aAmong 646 parous women.

  • bAmong 693 ever users of oral contraceptives.

  • cAverage intake for 1991 and 1995.