Table 1.

Characteristics at blood collection by leptin quartiles among cases and controls in the Nurses' Health Study II, 1996–2005

 Leptin quartiles, ng/mL
≤9.389.39–16.1916.2–26.69≥26.7
N245246251224
Median leptin, ng/mL6.412.220.435.9
Age, y43.1 (4.1)43.8 (3.8)43.9 (4.1)44.5 (3.6)
Height, inches65.3 (2.5)64.9 (2.6)64.9 (2.6)65.0 (2.5)
BMI at age 18 y, kg/m220.1 (1.9)20.4 (2.2)20.6 (2.8)22.7 (3.6)
BMI at blood draw, kg/m221.1 (1.9)23.2 (2.4)25.4 (3.4)31.6 (6.3)
Age at menarche, y12.9 (1.5)12.5 (1.4)12.4 (1.4)12.0 (1.3)
Nulliparous, %21.318.117.021.0
Age at first birth, y26.7 (4.4)27.2 (4.5)26.8 (4.7)26.5 (4.9)
Number of children, among parous women2.2 (0.8)2.4 (1.0)2.2 (0.9)2.2 (1.0)
Physical activity, MET/wk28.8 (39.4)17.6 (17.5)17.6 (18.3)15.1 (20.0)
Family history of breast cancer, %8.612.212.011.6
History of benign breast disease, %20.017.517.116.5
Ever used oral contraceptives, %83.387.885.787.5
Premenopausal at diagnosis, %85.789.883.778.6

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

Abbreviation: MET, metabolic equivalent.