Table 2.

Characteristics at blood collection of cases and their matched controls in the Nurses' Health Study II, 1996–2005

CasesControls
N330636
Age, y44.1 (4.0)43.6 (3.9)
Height, inches65.2 (2.6)64.9 (2.6)
BMI at age 18 y, kg/m220.8 (3.0)21.0 (2.8)
BMI at blood draw, kg/m224.9 (4.8)25.4 (5.7)
Age at first birth, y27.1 (4.6)26.7 (4.6)
Number of children, among parous women2.2 (0.8)2.3 (0.9)
Physical activity, MET/wk17.6 (21.2)21.0 (28.1)
Family history of breast cancer, %15.58.8
History of benign breast disease, %21.815.7
Age at menarche, y12.5 (1.4)12.5 (1.5)
Nulliparous, %22.717.6
Ever used oral contraceptives, %84.287.0
Premenopausal at diagnosis, %83.984.9
Median leptin (10th–90th percentile), ng/mL15.5 (6.5–33.8)16.2 (5.4–41.4)
 Luteal phase sample14.1 (6.5–32.9)15.9 (5.6–42.0)
 Untimed sample17.1 (6.6–46.4)17.3 (4.5–40.3)

NOTE: Data represent mean (SD) unless otherwise indicated.

Abbreviation: MET, metabolic equivalent.