. Author manuscript; available in PMC: 2013 Nov 1.

Published in final edited form as: Breast Cancer Res Treat. 2012 Sep 28;136(1):277–287. doi: 10.1007/s10549-012-2240-0

Table 1.

Characteristics of the study population (NHSII, n=352).

	Mean (SD) or %
Age at urine collection, y	42.6 (4.0)
Age at mammography, y	44.0 (3.9)
Average percent mammographic density	43.5 (19.1)
Average dense area, cm²	97.7 (49.4)
Average nondense areas, cm²	144.2 (86.2)
Body mass index at urine collection, kg/m²	25.0 (5.3)
Age at menarche 12, %	46.6
Nulliparous, %	18.2
Number of children^*	2.3 (0.9)
Age at first birth, y^*	26.8 (4.5)
Family history of breast cancer, %	7.4
Alcohol consumption, g/d	3.5 (5.6)

NHSII; Nurses' Health Study II

among parous women only.